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Evidence record

How much of our own ocean have we seen?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

  • Source checked: 34
  • A judgement, not a fact: 11
  • Partly checked: 3
  • Presented as open: 1

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A question of measurement that turns on definitions: how much of the ocean has been mapped, and how much seen, depends on what counts as mapping or seeing. The page separates the figures rather than choosing one.

  • There is one number for how much of the ocean we have seen

    Contested

    The page argues there is not: satellites cover all of it, sonar 28.7 per cent, cameras under 0.001 per cent of the deep seafloor, and "explored" is defined differently by different bodies.

  • Seeing the seafloor is what exploring it means

    Contested

    NOAA says the seafloor is not explored until it is seen; Bell and others count mapping, sampling and environmental data as exploration too.

  • The seafloor can be completely mapped

    Open

    Seabed 2030 aims to map all of it by 2030 and its founders judged the effort reachable; at the pace reported in 2026 it would take decades.

How the question is labelled

Claim: The unmapped seafloor

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Unmapped sea

Kind
Framing. Signposting. It asserts nothing a source could check.

The question

Claim: We have better maps of Mars than of the bottom of our own planet.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Coverage and resolution: nearly all of Mars is imaged at a few metres per pixel, while 28.7 per cent of the seafloor is mapped at high resolution and the rest only from orbit.

What this does not establish

The comparison is about maps, not about how much has been visited or studied. It is the judgement of the Seabed 2030 leads in 2018, when less than 15 per cent of the seafloor had been sampled for depth; the Mars mosaic is imagery rather than a depth measurement.

Later work looked for

Crossref, 2022 on, "global CTX mosaic Mars": Dickson and others 2024 describe a contiguous global mosaic at about 5 to 6 metres per pixel, which strengthens the comparison; the seafloor figure has risen to 28.7 per cent, still far below.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: Most of the seafloor has never been mapped at high resolution, and a far smaller fraction has ever been observed directly.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

Later work looked for

Seabed 2030 news, April to July 2026: the 20 April 2026 figure is the latest; the next grid is due in 2027. NOAA’s page was updated the same day and carries the same figure.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: The gap between “surveyed” and “seen” is the interesting part.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s own judgement, following from the two NOAA figures, 28.7 per cent mapped and less than 0.001 per cent of the deep seafloor seen.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: A NOAA fact page from 2009 said “we have explored less than five percent of the ocean”, and called the rest “unseen by human eyes”.

Kind
Quotes a source. The words of a named text, checked against the source.
Review
Source checked. The cited passage was read, and it says this.

NOAA’s current page puts the seen fraction of the deep seafloor at less than 0.001 per cent, and treats mapping and seeing separately.

  • Supports

    To date, we have explored less than five percent of the oceanheadline and paragraph 1 (archived 24 February 2011; page revised 13 January 2009)

    Cited · Link refuses automated checks, 19 October 2026 · Read in full, 24 September 2026

    The source reads: To date, we have explored less than five percent of the ocean ... Yet for all of our reliance on the ocean, 95 percent of this realm remains unexplored, unseen by human eyes.

What this does not establish

The archived page does not say how the five per cent was measured. It shows that NOAA used the figure; it does not show how widely it was repeated elsewhere.

Corrected

24 September 2026. Previously: “The sentence “we have explored only five percent of the ocean” gets repeated constantly, usually without anyone saying what exploring means.” The quotation had no source and was not verbatim, and "repeated constantly" could not be sourced. The slogan is quoted from where it was published, NOAA’s own fact page, in its own words.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: It is worth being precise, because the precise version is stranger than the slogan.

Kind
Framing. Signposting. It asserts nothing a source could check.

What the numbers actually mean

Claim: What the numbers actually mean

Kind
Framing. Signposting. It asserts nothing a source could check.

Mapped is not the same as seen

Claim: Mapped is not the same as seen

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

NOAA draws the same line: it counts mapping and seeing separately and says the seafloor is not explored until it has been seen.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: Satellite altimetry gives us a low-resolution shape for the entire seafloor by measuring how seafloor mass deforms the sea surface.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

Strictly the satellites measure the height of the sea surface, which the gravity of seafloor topography raises and lowers; depth is then inferred.

  • Supports

    Seafloor Mapping – The Challenge of a Truly Global Ocean BathymetrySatellite Altimetry, p. 3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Altimeters do not directly measure ocean depth, but the height of the ocean’s surface, which is affected, among other things, by the gravitational effects of topographic features on the seafloor.

  • Supports

    How much of the ocean has been explored?paragraph 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: While the entire seafloor has been mapped using data collected from satellites, these data provide only a general picture of what’s there.

Later work looked for

How the method works; not a finding later work revises. Crossref, 2023 on, "SWOT marine gravity": Yu and others 2024 expect the SWOT swath altimeter to sharpen the resolution, which does not change the present figure.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: This is why world ocean maps exist at all.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Global compilations fill the unsurveyed ocean with depths predicted from altimetry, which is what makes a complete-looking world map possible.

Claim 11 · checked 24 September 2026 · AI-assisted audit

Claim: The resolution is coarse, features smaller than several kilometres are invisible.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

The limit depends on the water depth: Mayer and others put it at about twice the local depth, about 8 km on average; Wölfl and others give 6 to 9 km under ideal conditions in the deep ocean.

Later work looked for

How the method works; not a finding later work revises. Crossref, 2023 on, "SWOT marine gravity": Yu and others 2024 expect the SWOT swath altimeter to sharpen the resolution, which does not change the present figure.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: High-resolution mapping needs a multibeam sonar, usually on a ship, sweeping a strip a few times as wide as the water is deep at around ten kilometres an hour.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

  • Supports

    The Nippon Foundation–GEBCO Seabed 2030 Project: The Quest to See the World’s Oceans Completely Mapped by 2030section 2.3, What Is the Magnitude of the Task?

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Model

    The source reads: this average water depth is multiplied by a factor representing the projection of the swath width of a multibeam system on the seafloor using the conservative estimate of 3.5 times the water depth, and; (3) the speed of the survey vessel is considered to be 7.5 knots (~10 km/h).

What this does not establish

The swath and the speed are the planning assumptions Mayer and others used to estimate the task, which they call conservative, not measurements of any one survey.

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “High-resolution mapping requires a ship with a multibeam sonar, travelling slowly.” NOAA says the sonars are "usually" mounted on ships, and autonomous vehicles carry them too (Wölfl and others 2019). "Travelling slowly" is replaced with the swath and speed Mayer and others 2018 use.

Claim 13 · checked 24 September 2026 · AI-assisted audit

Claim: As of April 2026 Seabed 2030 counted 28.7 per cent of the seafloor as mapped, with almost five million square kilometres added in the preceding year.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Global seabed mapping reaches new milestone as five million square kilometres added in a yearparagraph 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Measurement

    The source reads: The Nippon Foundation-GEBCO Seabed 2030 Project today announces that 28.7% of the world’s ocean floor has now been mapped, with almost five million square kilometres of data added over the past year.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

  • Context

    Global seabed mapping reaches new milestone as five million square kilometres added in a yearparagraph 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Over the past year alone, a further five million square kilometres of data have been incorporated into the GEBCO Grid.

  • Context

    Global seabed mapping reaches new milestone as five million square kilometres added in a yearhighlights of the past year

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Expanded coastal mapping through datasets such as the Global Coastal SDB Dataset from Copernicus/EOMAP

  • Context

    IHO Data Centre for Digital BathymetryCenter Overview; the archive that feeds the GEBCO grid

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: The DCDB archive includes over 30 terabytes (compressed) of primarily unedited single and multibeam bathymetric data contributed by industry, government, academia, and crowdsourced efforts.

What this does not establish

Seabed 2030 compiles its grid from single-beam as well as multibeam soundings, and the 2026 update added satellite-derived depths near coasts; NOAA describes the same figure as multibeam mapping.

Later work looked for

Seabed 2030 news, April to July 2026: the 20 April 2026 figure is the latest; the next grid is due in 2027. NOAA’s page was updated the same day and carries the same figure.

Corrected

24 September 2026. Previously: “As of April 2026 that covered 28.7 per cent of the seafloor, with almost five million square kilometres added in the preceding year.” The figure is Seabed 2030’s count of its compiled grid, which includes data other than ship multibeam surveys (the 2026 update names satellite-derived bathymetry among its additions). It is now attributed.

Claim 14 · checked 24 September 2026 · AI-assisted audit

Direct observation is a much smaller number

Claim: Direct observation is a much smaller number

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

Later work looked for

Crossref, 2024 on, "visual coverage deep seafloor": Bell and others 2025 (Science Advances) is the compilation behind a figure of this size and agrees with it; it now appears on the page.

Claim 15 · checked 24 September 2026 · AI-assisted audit

Claim: Actually looking (with a camera, a submersible, or a remotely operated vehicle) covers a far smaller fraction than sonar mapping does.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorResults

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: To quantify the visually explored deep seafloor, defined here as the area of seafloor imaged by a vehicle with optical imaging capabilities

Later work looked for

Crossref, 2024 on, "visual coverage deep seafloor": Bell and others 2025 (Science Advances) is the compilation behind a figure of this size and agrees with it; it now appears on the page.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: NOAA puts it at less than a thousandth of one per cent of the deep seafloor, an area about the size of Rhode Island, and more than nine tenths of the ocean is deep.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

NOAA counts the deep ocean as everything below 200 metres.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

Later work looked for

Crossref, 2024 on, "visual coverage deep seafloor": Bell and others 2025 (Science Advances) is the compilation behind a figure of this size and agrees with it; it now appears on the page.

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: A 2025 compilation of about 44,000 deep dives reached the same figure; its authors say it may be an underestimate, and that even ten times larger it would be under a hundredth of one per cent.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: Sixty-six percent of the entire planet is deep ocean (≥200 m), and our data show that we have visually observed less than 0.001%, a total area approximately a tenth of the size of Belgium. Data gathered from approximately 44,000 deep-sea dives

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorResults

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: these estimates may substantially underrepresent the explored seafloor ... even if off by a full order of magnitude, less than one-hundredth of 1% of the seafloor has any visual records.

What this does not establish

An estimate from dive records and assumed fields of view of 10 to 20 metres. Classified, commercial and embargoed dives are missing, and camera surveys by autonomous vehicles were left out, so the authors expect it to be low.

Later work looked for

Crossref, 2024 on, "visual coverage deep seafloor": Bell and others 2025 (Science Advances) is the compilation behind a figure of this size and agrees with it; it now appears on the page.

Corrected

24 September 2026. Previously: “” The page gave the figure without the study that measures it or its uncertainty. Added from Bell and others 2025.

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: The difference is partly geometry.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the widths in the next sentence: a camera strip of 10 to 20 metres against a sonar swath of kilometres.

Corrected

24 September 2026. Previously: “The deep ocean is also expensive to visit, which is most of why the second number is so much smaller than the first: every square kilometre of it is a ship, a crew and a vehicle in the water.” No source attributes most of the gap to cost. Cameras see a strip 10 to 20 metres wide because light does not carry through seawater (Bell and others 2025; Mayer and others 2018), while sonar sweeps a swath several times the depth. The cost is kept, as one reason rather than most of it.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: Light carries tens of metres through seawater at best, so a camera near the bottom sees a strip ten or twenty metres wide, while a ship’s sonar sweeps a swath several times as wide as the water is deep.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

The widths are the assumptions of the studies (10 to 20 metres for a camera, 3.5 times the depth for a sonar), not measurements of every dive or survey.

Later work looked for

How the instruments work; not a finding later work revises.

Corrected

24 September 2026. Previously: “” Added to give the physical reason for the gap, which the page had put down to cost alone.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: And looking is expensive: every dive is a ship, a crew and a vehicle in the water.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Bell and others describe the data as substantially expensive to gather; Wölfl and others call the time and people of ship-based work a considerable cost.

Corrected

24 September 2026. Previously: “every square kilometre of it is a ship, a crew and a vehicle in the water.” Kept as one reason for the gap rather than most of it; "every square kilometre" became "every dive", since a dive sees far less than a square kilometre.

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: Three different things the word explored is used for

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: 100%

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: While the entire seafloor has been mapped using data collected from satellites, these data provide only a general picture of what’s there.

Later work looked for

NOAA page, updated 20 April 2026: still says the entire seafloor has been mapped from satellites.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: Shape, from orbit

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Satellite altimetry covers all of it, and cannot resolve anything smaller than several kilometres.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Seafloor Mapping – The Challenge of a Truly Global Ocean BathymetrySatellite Altimetry, p. 3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Altimetry data have far lower horizontal resolution than ship’s bathymetry and provide depth estimates which are inherently under-determined. They can, however, reveal large geomorphological features of the ocean floor.

  • Supports

    The Nippon Foundation–GEBCO Seabed 2030 Project: The Quest to See the World’s Oceans Completely Mapped by 2030section 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: Considering that the recent estimate of the mean world ocean depth is ~3.9 km [ 1], the average achievable resolution is on the order of 8 km.

  • Supports

    How much of the ocean has been explored?paragraph 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: While the entire seafloor has been mapped using data collected from satellites, these data provide only a general picture of what’s there.

What this does not establish

The resolution limit depends on water depth, about twice the local depth.

Later work looked for

How the method works; not a finding later work revises. Crossref, 2023 on, "SWOT marine gravity": Yu and others 2024 expect the SWOT swath altimeter to sharpen the resolution, which does not change the present figure.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: 28.7%

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

  • Supports

    Global seabed mapping reaches new milestone as five million square kilometres added in a yearparagraph 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Measurement

    The source reads: The Nippon Foundation-GEBCO Seabed 2030 Project today announces that 28.7% of the world’s ocean floor has now been mapped, with almost five million square kilometres of data added over the past year.

Later work looked for

Seabed 2030 news, April to July 2026: the 20 April 2026 figure is the latest; the next grid is due in 2027. NOAA’s page was updated the same day and carries the same figure.

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: Mapped at high resolution

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

  • Context

    Global seabed mapping reaches new milestone as five million square kilometres added in a yearhighlights of the past year

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Expanded coastal mapping through datasets such as the Global Coastal SDB Dataset from Copernicus/EOMAP

  • Context

    IHO Data Centre for Digital BathymetryCenter Overview; the archive that feeds the GEBCO grid

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: The DCDB archive includes over 30 terabytes (compressed) of primarily unedited single and multibeam bathymetric data contributed by industry, government, academia, and crowdsourced efforts.

What this does not establish

Seabed 2030’s grid also draws on single-beam soundings, and its 2026 update added satellite-derived depths near coasts.

Later work looked for

Seabed 2030 news, April to July 2026: the 20 April 2026 figure is the latest; the next grid is due in 2027. NOAA’s page was updated the same day and carries the same figure.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: Multibeam sonar, usually from a ship.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

Later work looked for

Seabed 2030 news, April to July 2026: the 20 April 2026 figure is the latest; the next grid is due in 2027. NOAA’s page was updated the same day and carries the same figure.

Corrected

24 September 2026. Previously: “Multibeam sonar from a ship, travelling slowly.” NOAA says "usually mounted to ships"; "travelling slowly" had no source.

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: NOAA, April 2026.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

Later work looked for

Seabed 2030 news, April to July 2026: the 20 April 2026 figure is the latest; the next grid is due in 2027. NOAA’s page was updated the same day and carries the same figure.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: <0.001%

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: Sixty-six percent of the entire planet is deep ocean (≥200 m), and our data show that we have visually observed less than 0.001%, a total area approximately a tenth of the size of Belgium. Data gathered from approximately 44,000 deep-sea dives

Later work looked for

Crossref, 2024 on, "visual coverage deep seafloor": Bell and others 2025 (Science Advances) is the compilation behind a figure of this size and agrees with it; it now appears on the page.

Claim 30 · checked 24 September 2026 · AI-assisted audit

Claim: Observed directly

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Camera, submersible or remotely operated vehicle, of the deep seafloor.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorResults

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: To quantify the visually explored deep seafloor, defined here as the area of seafloor imaged by a vehicle with optical imaging capabilities

Later work looked for

Crossref, 2024 on, "visual coverage deep seafloor": Bell and others 2025 (Science Advances) is the compilation behind a figure of this size and agrees with it; it now appears on the page.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: NOAA, April 2026.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

The page carrying the figure was last updated on 20 April 2026.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

  • Supports

    How much of the ocean has been explored?page footer

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Last updated April 20, 2026

Later work looked for

Crossref, 2024 on, "visual coverage deep seafloor": Bell and others 2025 (Science Advances) is the compilation behind a figure of this size and agrees with it; it now appears on the page.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Why the figures disagree

Claim: Why the figures disagree

Kind
Framing. Signposting. It asserts nothing a source could check.

What the percentages actually mean

Claim: What the percentages actually mean

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Different agencies count differently: mapped at what resolution, observed by what instrument, explored to what standard.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Seabed 2030 counts "mapped to an adequate resolution"; Bell and others define explored seafloor as anywhere visual observation, mapping, sampling or environmental data exist; NOAA counts only what has been seen.

  • Supports

    About the Nippon Foundation–GEBCO Seabed 2030 ProjectOur Story, paragraph 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: In 2017, The Nippon Foundation and General Bathymetry Chart of the Ocean (GEBCO) came together ... at the time, only 6% had been mapped to an adequate resolution.

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorIntroduction, Visual observations are critical

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Here, we define “explored seafloor” as those locations where visual observations, seabed mapping, sampling, and environmental data collection exist

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: Figures from a thousandth of a per cent to a hundred all appear in reputable sources and they are not contradicting each other.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The same NOAA page gives both 28.7 per cent mapped and less than 0.001 per cent seen, and says the entire seafloor has been mapped from satellites.

  • Supports

    How much of the ocean has been explored?paragraph 5

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution technology ( multibeam sonar systems ), usually mounted to ships, that can reveal the seafloor in greater detail.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

  • Supports

    How much of the ocean has been explored?paragraph 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: While the entire seafloor has been mapped using data collected from satellites, these data provide only a general picture of what’s there.

Corrected

24 September 2026. Previously: “Figures from a fraction of a per cent to nearly thirty all appear in reputable sources and they are not contradicting each other.” Integrity pass: the range stopped at the multibeam 28.7 per cent, but the same page shows, and NOAA states, that satellite altimetry has mapped the entire seafloor, so the figures in reputable sources run to a hundred. The low end is NOAA's and Bell and others' 0.001 per cent, a thousandth of a per cent.

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: They are measuring different things.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

  • Supports

    How much of the ocean has been explored?paragraph 6

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Reference work

    The source reads: We can’t say we’ve explored the seafloor until we’ve seen it, and explorers have seen less than 0.001% of the deep ocean seafloor – that’s roughly the size of Rhode Island. Since more than 90% of the ocean is deep ocean (i.e., deeper than 200 meters/656 feet)

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorIntroduction, Visual observations are critical

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Here, we define “explored seafloor” as those locations where visual observations, seabed mapping, sampling, and environmental data collection exist

Claim 38 · checked 24 September 2026 · AI-assisted audit

What lies on the unsurveyed parts

Claim: What lies on the unsurveyed parts

Kind
Framing. Signposting. It asserts nothing a source could check.

What is on the parts nobody has surveyed

Claim: What is on the parts nobody has surveyed

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Seamounts are still being found.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Global Distribution and Morphology of Small Seamountsabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: We used the latest grid of VGG to update and refine the global seamount catalog; we identified 19325 new seamounts, expanding a previously published catalog having 24643 seamounts.

  • Supports

    Global Distribution and Morphology of Small Seamountssection 1.1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: The knowledge of the global distribution of seamounts is still incomplete because only 20% of the seafloor has been mapped by ships

Later work looked for

Crossref, 2023 on, "seamounts SWOT" and "global distribution of seamounts": Yu and others 2024 (abstract) expect thousands more from SWOT; a 2026 conference abstract (Wang and Watts) reports machine learning finding up to twice as many in two pilot areas. The page now reports the SWOT expectation.

Corrected

24 September 2026. Previously: “Seamounts are being discovered continuously.” "Continuously" claimed more than the catalogue updates show; the sentence now states what they do.

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: One reanalysis of satellite gravity data identified 19,325 that were not in the catalogue, against 24,643 that were,

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Global Distribution and Morphology of Small Seamountsabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: We used the latest grid of VGG to update and refine the global seamount catalog; we identified 19325 new seamounts, expanding a previously published catalog having 24643 seamounts.

What this does not establish

Found in satellite gravity data, not surveyed by ship; the authors estimate the heights of small seamounts to about 270 metres.

Later work looked for

Crossref, 2023 on, "seamounts SWOT" and "global distribution of seamounts": Yu and others 2024 (abstract) expect thousands more from SWOT; a 2026 conference abstract (Wang and Watts) reports machine learning finding up to twice as many in two pilot areas. The page now reports the SWOT expectation.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: and a 2024 study by two of the same authors expects the SWOT satellite to reveal thousands more.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Accuracy and Resolution of SWOT Altimetry: Foundation Seamountsabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Measurement

    The source reads: SWOT promises a substantial leap in marine gravity accuracy and resolution, uncovering previously uncharted details of the seafloor, including thousands of uncharted seamounts.

What this does not establish

A prediction from the satellite’s tested accuracy at one group of seamounts, not a count. Only the abstract was read.

Later work looked for

Crossref, 2023 on, "seamounts SWOT" and "global distribution of seamounts": Yu and others 2024 (abstract) expect thousands more from SWOT; a 2026 conference abstract (Wang and Watts) reports machine learning finding up to twice as many in two pilot areas. The page now reports the SWOT expectation.

Corrected

24 September 2026. Previously: “and there is no reason to think that has stopped.” The page’s own inference is replaced with what the researchers expect, from Yu and others 2024.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: Many appear rich in life,

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Global Distribution and Morphology of Small Seamountssection 1.1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: From an ecological perspective, seamounts are centers for diverse biological communities.

  • Qualifies

    Paradigms in seamount ecology: fact, fiction and futureabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field

    The source reads: We find plausible evidence that seamounts are stepping stones for dispersal, oases of abundance and biomass, and hotspots of species richness. Nonetheless, the poor sampling coverage of these discrete but globally distributed environments prevents us from accepting these ideas as paradigms.

What this does not establish

A 2010 review found the evidence for seamounts as oases and hotspots of species plausible, but too thinly sampled to accept as established.

Later work looked for

Crossref, 2011 on, "seamount endemism": nothing found that reverses the 2010 review.

Corrected

24 September 2026. Previously: “Each one is a habitat, often with endemic species.” Not every seamount has been shown to be a habitat of note, and endemism on seamounts is not supported by the weight of evidence (Rowden and others 2010).

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: though a 2010 review found the idea that seamounts are islands of endemic species unsupported by the evidence.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Paradigms in seamount ecology: fact, fiction and futureabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field

    The source reads: the generalizations that seamounts are island habitats with highly endemic faunas that comprise unique communities distinct in species composition from other deep‐sea habitats ... are not supported by the weight of existing evidence.

What this does not establish

Only the abstract was read. The review also found that seamount communities are vulnerable to bottom trawling.

Later work looked for

Crossref, 2011 on, "seamount endemism": nothing found that reverses it.

Corrected

24 September 2026. Previously: “” Added to report the review that tests the endemism the page had asserted.

Claim 45 · checked 24 September 2026 · AI-assisted audit

How much we are changing before we describe it

Claim: How much we are changing before we describe it

Kind
Open question. Something the page says is not known.
Review
Presented as open. The page says this is unresolved, and the review found that it is.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: Bottom trawling and climate-driven changes in ocean chemistry are already altering deep habitats that have never been surveyed,

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Paradigms in seamount ecology: fact, fiction and futureabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Review of the field

    The source reads: We find the assertions that seamount communities are vulnerable to fishing, and that these communities have high sensitivity and low resilience to bottom trawling disturbance are well supported by existing data.

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorabstract; Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: our data show that we have visually observed less than 0.001% ... These impacts have been well documented and broadly grouped into three main categories: disposal of litter and chemical pollution, exploitation of biological and geological resources, and climate change and ocean acidification

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorIntroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: While climate change is already affecting the deep ocean, deep-sea mining and marine carbon dioxide removal (mCDR) also have the potential to cause irreparable damage

What this does not establish

The trawling evidence is from a review read only as an abstract. That the altered habitats were never surveyed is the page’s inference from how little has been seen.

Later work looked for

Crossref, 2024 on, "deep sea climate change impacts": Bell and others 2025 summarise warming, deoxygenation and acidification as already affecting the deep ocean; nothing found that changes it.

Corrected

24 September 2026. Previously: “Deep-sea mining, bottom trawling and climate-driven changes in ocean chemistry are altering habitats that have never been surveyed.” Commercial deep-sea mining has not begun, and Bell and others 2025 describe its damage as potential. The passage had no sources; it now cites Bell and others 2025 and Rowden and others 2010.

Claim 47 · checked 24 September 2026 · AI-assisted audit

Claim: and deep-sea mining could add to them.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorIntroduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: While climate change is already affecting the deep ocean, deep-sea mining and marine carbon dioxide removal (mCDR) also have the potential to cause irreparable damage

Later work looked for

Not a finding with a figure; Bell and others 2025 is the most recent source read.

Corrected

24 September 2026. Previously: “Deep-sea mining, bottom trawling and climate-driven changes in ocean chemistry are altering habitats that have never been surveyed.” Mining moved from present to potential; see claim 47.

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: The baseline against which those changes would be measured does not exist for most of the seafloor.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from how little of the deep seafloor has been seen, less than 0.001 per cent, and from how unevenly: most dives were near three countries.

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: This small and biased sample is problematic when attempting to characterize, understand, and manage a global ocean.

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Earth and its record · Measurement

    The source reads: Sixty-six percent of the entire planet is deep ocean (≥200 m), and our data show that we have visually observed less than 0.001%, a total area approximately a tenth of the size of Belgium. Data gathered from approximately 44,000 deep-sea dives

  • Supports

    How little we’ve seen: A visual coverage estimate of the deep seafloorabstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Sixty-five percent of all in situ visual seafloor observations in our dataset were within 200 nm of only three countries: the United States, Japan, and New Zealand.

Claim 49 · checked 24 September 2026 · AI-assisted audit

What would close the gap

Claim: What would close the gap

Kind
Framing. Signposting. It asserts nothing a source could check.

A complete map is the target for 2030

Claim: A complete map is the target for 2030

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    About the Nippon Foundation–GEBCO Seabed 2030 ProjectOur Story, paragraph 3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: the two organisations have committed to building the necessary technical, scientific, and management framework to compile all available seabed mapping information into a seamless digital map of the world’s ocean floor by 2030.

Corrected

24 September 2026. Previously: “Complete mapping is achievable this decade” The target is the project’s aim; at the pace it reports, a complete map by 2030 is not in prospect. The heading now says what the source says.

Claim 51 · checked 24 September 2026 · AI-assisted audit

Claim: Seabed 2030 aims to compile all available seabed mapping information into a seamless map of the ocean floor by 2030,

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    About the Nippon Foundation–GEBCO Seabed 2030 ProjectOur Story, paragraph 3

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: the two organisations have committed to building the necessary technical, scientific, and management framework to compile all available seabed mapping information into a seamless digital map of the world’s ocean floor by 2030.

Claim 52 · checked 24 September 2026 · AI-assisted audit

Claim: pooling data contributed by industry, government, academia and crowdsourced efforts alongside dedicated surveys.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Seabed 2030 announcement, April 2026: 220 organisations have now contributed; nothing that changes it.

Claim 53 · checked 24 September 2026 · AI-assisted audit

Claim: When the project began in 2017, 6 per cent of the seafloor had been mapped to an adequate resolution.

Kind
Historical claim. A statement about the past that historical evidence can test.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    About the Nippon Foundation–GEBCO Seabed 2030 ProjectOur Story, paragraph 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: In 2017, The Nippon Foundation and General Bathymetry Chart of the Ocean (GEBCO) came together ... at the time, only 6% had been mapped to an adequate resolution.

Corrected

24 September 2026. Previously: “” Added with the next sentence to replace "the map is filling in faster than at any point in history", which no source states.

Claim 54 · checked 24 September 2026 · AI-assisted audit

Claim: At last year’s pace of about five million square kilometres, the remaining quarter of a billion would take about fifty years,

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

104 million square kilometres is 28.7 per cent, so the seafloor is about 362 million and about 258 million remain; at five million a year that is about 52 years.

What this does not establish

Arithmetic on one year’s pace. Mayer and others expected new technology to shorten the task, and newly shared data can add large areas at once.

Later work looked for

Seabed 2030 news, April to July 2026: the 20 April 2026 figure is the latest; the next grid is due in 2027. NOAA’s page was updated the same day and carries the same figure.

Corrected

24 September 2026. Previously: “Whether the target is met, the trajectory is real: the map is filling in faster than at any point in history.” No source states that mapping is faster than ever. The project’s own figures give the pace, and the pace does not reach the target.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: so meeting the target means mapping more than ten times as fast.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

About 258 million square kilometres in the four years to 2030 is about 65 million a year, thirteen times the pace reported for the year to April 2026.

Corrected

24 September 2026. Previously: “Whether the target is met, the trajectory is real: the map is filling in faster than at any point in history.” See claim 55.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Autonomous vehicles could change what observation costs

Claim: Autonomous vehicles could change what observation costs

Kind
Hypothesis. A proposed explanation, not an established one.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Wynn and others call autonomous systems a potentially attractive way to cut costs; no source read measures a cost per square kilometre observed.

Corrected

24 September 2026. Previously: “Autonomous vehicles change what observation costs” Stated as a change already made; the sources describe a potential.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: Autonomous underwater vehicles work independently of the ship that launched them, which is what lets them into places a hull cannot follow: the deepest hydrothermal vents, the underside of polar ice.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2014 on, "autonomous underwater vehicle seafloor mapping": Wölfl and others 2019 (a review from the Seabed 2030 community) confirm the resolution advantage and add that AUVs are still slow over large areas; the page now says so.

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: In deep water they also image the seafloor at resolutions a surface vessel cannot reach.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2014 on, "autonomous underwater vehicle seafloor mapping": Wölfl and others 2019 (a review from the Seabed 2030 community) confirm the resolution advantage and add that AUVs are still slow over large areas; the page now says so.

Claim 59 · checked 24 September 2026 · AI-assisted audit

Claim: For now they are slower than ships and inefficient over large areas, which several working together can offset.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Seafloor Mapping – The Challenge of a Truly Global Ocean BathymetryAutonomous Systems, p. 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The deployment of these near-bottom mapping systems is currently still inefficient for the mapping of large areas, partly because of their slow speeds compared to ships. However, in the case of AUVs this can be compensated for by multiple vehicles working in tandem.

Later work looked for

Crossref, 2014 on, "autonomous underwater vehicle seafloor mapping": Wölfl and others 2019 (a review from the Seabed 2030 community) confirm the resolution advantage and add that AUVs are still slow over large areas; the page now says so.

Corrected

24 September 2026. Previously: “” Added: the review the page relies on for the next sentence’s hope also records this limit (Wölfl and others 2019).

Claim 60 · checked 24 September 2026 · AI-assisted audit

Claim: If the cost per square kilometre of direct observation falls far enough, the gap between mapped and seen could narrow in a way that ship-based exploration never could.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A conditional the page draws from the reviews’ account of autonomous vehicles.

  • Supports

    Autonomous Underwater Vehicles (AUVs): Their past, present and future contributions to the advancement of marine geosciencesection 1, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: such as rapidly increasing vessel fuel oil costs ... a potentially attractive proposition to organisations responsible for large-scale and cost-effective marine data collection

  • Supports

    Seafloor Mapping – The Challenge of a Truly Global Ocean BathymetryAutonomous Systems, p. 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: The deployment of these near-bottom mapping systems is currently still inefficient for the mapping of large areas, partly because of their slow speeds compared to ships. However, in the case of AUVs this can be compensated for by multiple vehicles working in tandem.

  • Supports

    Seafloor Mapping – The Challenge of a Truly Global Ocean BathymetryAutonomous Systems, p. 4

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field

    The source reads: at present, they are not able to make ship-based surveys obsolete, since it is still essential to roughly understand the bathymetry of an area before a submersible can be sent down toward the seafloor.

  • Context

    How little we’ve seen: A visual coverage estimate of the deep seafloorMethods, method 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: we did not include AUV deployments in this calculation understanding that this decision will likely lead to an underestimation of the area covered.

What this does not establish

Wölfl and others 2019 say autonomous vehicles cannot yet replace ship surveys, and Bell and others 2025 left their camera surveys out of the count of what has been seen.

Corrected

24 September 2026. Previously: “the gap between mapped and seen could close” No source read supports closing the gap; near-bottom vehicles are still slow over large areas (Wölfl and others 2019).

Claim 61 · checked 24 September 2026 · AI-assisted audit

What was read