More than 7,500 people have stood on top of Mount Everest. In a good May there is a queue on the ridge. The photographs coming back look less like exploration than like commuting.
In recent years, there has been a growing interest in exploring the deep ocean and understanding its mysteries.
Fewer than thirty people have ever been to the deepest point of the ocean.
The exact number is disputed. The published list of descents to Challenger Deep runs to 22 people as of July 2022. Other counts say 27. Nobody keeps a proper register, which tells you something on its own.
In May 2025 a team at the Ocean Discovery League put the whole thing in proportion. They worked through 43,681 dive records going back to 1958. Their finding: humans have laid eyes on less than 0.001 per cent of the deep seafloor. The area we have actually looked at is about the size of Rhode Island. Call it a tenth of Belgium.
The deep sea is two thirds of the surface of this planet.
New technologies are making it possible for scientists to embark on missions focused on exploring the deep ocean.
If you are thinking that none of this touches your life, hold that thought for two minutes. It runs your internet connection, it holds the heat we have added to the planet, and it is quietly telling us how much trouble the sea outside your own window is in, especially as we venture into exploring the deep ocean.
“Mapped” is not the same as seen
You will read that the ocean floor has been mapped. That is true in a narrow sense, and misleading in a useful one.
As of 20 April 2026, the Seabed 2030 project reported 28.7 per cent of the ocean floor mapped to modern standards. That is about 104 million square kilometres, five million of them added in a single year.
The rest sits on charts built from satellite measurements. A seamount is heavy, so it pulls water towards it and raises a slight bulge in the sea surface above. Satellites read the bulge and infer the mountain. Clever, and it works.
Through innovative methods, researchers are enhancing their efforts in exploring the deep ocean, revealing new insights about our planet.
It also has a resolution measured in kilometres. Put that method over land and you would get a map with no buildings on it.
So there are two numbers, and they are not versions of each other. Twenty-nine per cent has been measured for shape. One thousandth of one per cent has been looked at.
The looking was done from a short list of addresses, too. Sixty-five per cent of those observations fall within 200 nautical miles of three countries: the United States, Japan and New Zealand. Five countries made 97 per cent of the dives. Whatever anyone believes about the deep sea, they believe it from a sample chosen by who owned a ship.
What the deep sea already does for you
Start with the least romantic thing down there. Cables.
Between 95 and 99 per cent of the data that crosses an ocean travels through fibre-optic cable lying on the seabed. Not satellites. Cable. Your bank transfer, your video call, the page you are reading. More than 600 cable systems are in service or planned, running well over a million kilometres in total.
They break about 200 times a year. Around 86 per cent of those faults come from fishing gear and ships’ anchors — not sabotage, just ordinary work happening on top of them. Repairs can take months, because the world’s repair fleet is small and ageing. When several cables in the Baltic were cut in late 2024, the reason that story mattered was not espionage. It was that a handful of lines on a seabed nobody has properly surveyed carry the economy of a region.
Knowing exactly where the seabed is, and what it is made of, is how those cables get routed, buried and protected. That is not an abstract public good. That is your Tuesday.
Then there is the heat.
The ocean has absorbed more than 90 per cent of the extra heat that greenhouse gases have trapped since the 1970s. Not the air. The water. The air is the small share.
We know that because of Argo: about 4,000 drifting robot floats that sink, measure and surface every ten days to radio their readings home. They stop at 2,000 metres. Below that, a separate fleet called Deep Argo does the same work at full ocean depth — and roughly 200 of a planned 1,200 floats exist, because the rest are not funded.
Read that again. The single largest store of the heat we have added to the planet is monitored by about a sixth of the instruments the scientists asked for.
Why Everest and not this
Everest is harder to breathe on and much easier to sell. It has a top.
A summit is a finishable object. You can photograph it, date it, and put a person’s name on it. They come home with a record. The deep ocean offers none of that. There is a deepest point, and reaching it finishes nothing, because the bottom was never the interesting part.
This is a general weakness in how big money gets spent, and it is worth saying plainly. We are much better at funding goals that can be completed than goals that can only be continued. A project with a finish line survives a change of government. A project that produces a slightly better map every year does not.
The dedicated NOAA Ocean Exploration budget was $46 million in the 2025 US fiscal year. NASA’s total request for 2026 was $24.4 billion. That is not a fair comparison — NASA does a hundred things, and ocean science draws on other budgets too. It is offered for the order of magnitude of attention, nothing more.
The afternoon in 1977 the textbooks changed
On 17 February 1977, a small crew took the submersible Alvin down 2,500 metres to the Galápagos Rift. They were investigating odd spikes in water temperature picked up by a towed camera sled. It was a geology trip.
In the last minutes of the dive they found clams the length of a forearm, packed around cracks in fresh volcanic rock, in water shimmering with heat.
Until that afternoon, biology rested on one assumption: life on Earth runs on sunlight. The vent communities do not. They run on chemosynthesis. Bacteria turn the chemistry venting out of the Earth’s crust into energy, and everything else eats the bacteria, or eats each other. More than 500 active vent fields have been found since.
Nobody proposed that expedition on the grounds that it might overturn the foundations of biology. They went to look at rocks.
That is the strongest argument for exploring, and it is also the weakest. It is the argument every unfunded project makes. You never know what we might find is the last line of a bad proposal exactly as often as it is the first line of a good one. It cannot tell the two apart. So the specific claims have to be taken one at a time.
The enzyme that came out of a hot crack in the seabed
Here is one that did pay, and nobody predicted it.
Thermococcus litoralis is a microbe that lives around hydrothermal vents. It is happiest at 85 to 88 degrees. Its DNA-copying enzyme survives eight hours at 95 degrees, and it proofreads its own work, so it makes several times fewer mistakes than the standard alternative.
That enzyme is sold as Vent polymerase, and it sits in molecular biology labs across the world. Its relatives came out of similar places. Copying DNA accurately, in a machine, at temperatures that would cook any normal protein, is a thing modern biology simply does — and part of the reason it can is that somebody went and looked in boiling water on the seabed.
No grant application predicted that. It came out of the same trip as the clams.
Energy — check whether they mean energy or metal
When the deep ocean is sold as an energy prospect, the thing on the table is usually not energy.
There is real fuel down there. Methane hydrates lock natural gas into an ice-like solid in seabed sediment. The awkwardness is not technical. Methane is fossil carbon, and a new source of fossil carbon is a strange thing to file under solutions to a problem caused by fossil carbon. Offshore oil drilling deeper is the same argument with better engineering.
What is actually being argued about is metal. Polymetallic nodules are lumps the size of a potato, made of manganese, nickel, cobalt and copper, lying loose on the abyssal plain. They are wanted for batteries.
That is a genuine connection to the energy transition. But it runs through a supply chain, not through a source of power, and the two claims carry completely different evidence. Spotting that swap is ordinary bullshit-detector work. When somebody says the deep sea will help solve the energy problem, the useful question is short: do you mean joules, or do you mean nickel?
Food — the biggest catch nobody is catching
One day we will probably fish the deep. It is worth understanding what that would mean before it happens rather than after.
In February 2014, a team led by Xabier Irigoien published acoustic results from a round-the-world voyage in Nature Communications. Their conclusion: the mass of fish in the twilight zone — the layer between roughly 200 and 1,000 metres — was at least ten times the standing estimate. Ten thousand million tonnes rather than one thousand million.
The number travelled fast. It deserves care.
In May 2019, Roland Proud and colleagues published a paper in the ICES Journal of Marine Science whose whole subject was how wide the uncertainty is. It runs to roughly an order of magnitude, depending on which assumptions you use.
The reason is that the estimate is built from sound. Sonar reads the echo bouncing off gas-filled swim bladders. Siphonophores are jelly-like animals that carry gas floats, and they return a similar echo without being fish at all. Get the mix wrong and the answer moves by a factor of ten.
Now suppose the high number is right. Two things follow that almost never appear next to the headline.
The first is what these animals are. Mostly lanternfish. Small, bony, oily, full of wax esters. They would not reach anyone’s plate as fish. They would be ground into fishmeal and fed to farmed salmon. That is a real industry. It is not the answer to human hunger that it gets described as.
The second is what they are already doing. Every night the twilight zone rises to feed near the surface. Every dawn it sinks again. In sinking, it carries carbon away from the atmosphere. The ocean takes up somewhere between a quarter and a third of the carbon dioxide we emit, and that nightly migration is part of the machinery that delivers it.
So the largest untapped source of protein on the planet may also be a working part of the system holding the climate down. Nobody knows the exchange rate between the two.
That is not an argument against ever fishing it. It is an argument for finding out the exchange rate first. And that is an exploration question, not a fisheries question.
Medicine, and the question of whose
The medicine cabinet is the part of the case you can check rather than believe.
Cytarabine, approved in 1969 and still used against leukaemia, came out of a Caribbean sponge. Ziconotide, approved in 2004 for severe chronic pain, is a synthetic copy of a peptide in the venom of a cone snail. Trabectedin, approved in 2015 for soft-tissue sarcoma, was isolated from a sea squirt. Eribulin, approved in 2010 for advanced breast cancer, comes from a sponge compound.
Two honest qualifications. Most of those animals live in shallow water, not the abyss. So they show that marine chemistry is unusually productive, rather than proving the deep specifically pays. And the road from collection to approval runs to decades, which makes this a poor argument for anyone who needs a return inside a budget cycle.
Then there is the question of who benefits.
In 2018, Robert Blasiak and colleagues traced who owns marine genetic patents, in Science Advances. Of 12,998 patented gene sequences from 862 marine species, 47 per cent were registered by a single company: BASF. That is more than the next 220 companies put together. Entities in ten countries held 98 per cent of the total.
The phrase benefits to humanity does a lot of unexamined work in writing on this subject. The first serious attempt to give it legal meaning arrived on 17 January 2026, when the High Seas Treaty came into force after passing sixty ratifications. One of its four main parts sets up a framework for sharing the benefits of genetic material taken from waters that belong to nobody. Whether it works is open. That it exists changes what the science argument is allowed to assume.
What the deep tells you about the sea outside your window
This is the part that matters most to people who will never go anywhere near a submersible.
Some deep-sea corals live for thousands of years. A black coral found in Hawaiian waters has been aged at more than 4,000. Certain black and bamboo corals lay down growth layers like tree rings, and the chemistry locked into each layer records the temperature, the acidity and the nutrients of the water it grew in.
That is an archive. It tells you what the ocean was like before us — and you cannot say how far something has fallen if nobody wrote down where the top was.
Which brings this home, literally.
Denmark is a green and comfortable country that thinks of itself as clean. In the period from late August to late September 2024, the National Centre for Environment and Energy at Aarhus University measured oxygen depletion across 11,000 square kilometres of Danish waters. It was the second largest area ever recorded there, beaten only by 2002. By late August 2025 the affected area was a fifth larger again than at the same point the year before, and in the worst spots the seabed was giving off hydrogen sulphide — the gas that smells of rotten eggs and kills almost everything that breathes.
Water without oxygen is not water with fewer fish in it. It is water with no fish in it at all.
That process, why it is getting worse while we spread less fertiliser, and the one time a dead zone was reversed at scale, are covered separately here.
The instruments that measured that, the models that explain it, and the baselines that prove it is abnormal all come from the same body of ocean science that sends robots into the abyss. It is one field. The reason anyone can say the inner Danish waters are in trouble is that somebody, over decades, did the unglamorous work of finding out what normal looked like.
That is the honest answer to what is in it for me. Not a treasure chest. A thermometer, a baseline and a witness.
The order of operations, which is where the argument lands
The question in the title is normally posed as exploring versus leaving it alone. That is not the choice in front of anybody.
The Clarion–Clipperton Zone is a stretch of Pacific abyssal plain roughly the size of Europe, and it is where the nodules are. In 2023, Muriel Rabone and colleagues at the Natural History Museum published the first species checklist for it in Current Biology. They recorded 5,578 species. An estimated 88 to 92 per cent of them have never been described. Not undiscovered — collected, photographed, and still without a name.
Nodules grow at roughly 1 to 10 millimetres per million years. Whatever is taken is taken on a human timescale and replaced on a geological one. This is one of the few industrial decisions where the word irreversible is being used literally.
We have exactly one long-run observation. In 1979, a test mining operation cut tracks into the seafloor of that zone. A team led by Daniel Jones went back in 2023 and published in Nature on 26 March 2025. Forty-four years on, the tracks are still there. Biodiversity is still below the untouched seafloor next door. But several groups of animals have begun to come back. It is neither the sterilisation some expected nor the recovery others promised. And it is one site.
Meanwhile the clock on the taking runs faster than the clock on the science. The International Seabed Authority was supposed to finish its mining code by 2023 and has not. At its July 2026 council meeting it extended an exploration contract for a subsidiary of The Metals Company. The same company has gone around the Authority and applied under United States law instead. NOAA received its amended application for an exploration licence and a commercial recovery permit on 19 March 2026, with a public hearing set for 13 October 2026.
So the describing and the taking are running side by side. That is the one arrangement which guarantees the information arrives too late to be used.
Dark oxygen, and how hard it is to know anything down there
On 22 July 2024, Andrew Sweetman and colleagues published a paper in Nature Geoscience. They reported oxygen being made at around 4,000 metres, in total darkness, apparently by the nodules themselves acting as natural batteries and splitting seawater.
If it holds, it unsettles the assumption that free oxygen requires photosynthesis. It also means the objects being scooped up are doing something nobody had accounted for.
It has not held cleanly. Five rebuttals have been published. One came from The Metals Company, which argued the oxygen could be trapped air or stray current in the equipment — and which has money riding on the answer. Others raised objections independently. Sweetman has conceded that some of the instruments involved held manganese oxide particles rather than nodules. On 8 April 2026, Nature Geoscience attached an Editor’s Note saying parts of the paper are under review by the editors.
The temptation is to pick a side. The discipline is not to.
In a place where a thousandth of a per cent has been seen, one startling result is a hypothesis, and the correct position is not yet. What can be said without waiting is this: both the claim and the loudest attack on it come from parties with something riding on the outcome. That is a fact about the state of the field, not a reason to trust either of them. When the evidence that would settle a question comes almost entirely from people who need a particular answer, the shortage of independent observation stops being an academic complaint. It becomes the whole problem.
So — is it a smart thing to be exploring the deep ocean?
Yes. And for a reason that has almost nothing to do with what we might find.
Every specific promise here comes back qualified. The energy case is mostly a metals case in borrowed clothes. The food case rests on an estimate with a factor of ten in it, attached to animals that may be doing a climate job worth more than the protein. The medical case is real, checkable and slow, and the rewards have landed in remarkably few hands. Taken one by one, not one of them would justify a serious programme on expected returns.
The case does not rest on any of them. It rests on what the alternative actually is.
Choosing not to explore does not mean leaving the deep ocean alone. The applications are filed. The contracts are extended. The hearing is scheduled. Choosing not to explore means taking from a place we cannot describe, on the strength of a sample gathered by five countries within sight of three coastlines.
Exploring the deep ocean is not the opposite of leaving it alone. It is the only thing that makes a decision to leave it alone possible, or defensible, or even meaningful.
That reframing is worth carrying past this subject, because it is how most big decisions are really shaped. The choice is rarely between acting and not acting. It is between acting with a description of what you are acting on, and acting without one.
And there are three small habits in here worth keeping. Know the difference between mapped and seen. When someone sells you an energy story, ask whether they mean joules or nickel. And when a number only ever comes from people who need it to say a particular thing, treat the shortage of independent evidence as the finding.
Everest could be climbed because it could be seen. The whole of it fitted in a photograph before anyone set out. Nothing about the deep sea fits in a photograph. We are 0.001 per cent of the way through looking, and the paperwork to start taking is already sitting with a regulator.
Sources
- Ocean Discovery League, How little we’ve seen: A visual coverage estimate of the deep seafloor, Science Advances (May 2025)
- Nippon Foundation–GEBCO Seabed 2030, Global seabed mapping reaches new milestone as five million square kilometres added in a year (20 April 2026)
- Xabier Irigoien et al., Large mesopelagic fishes biomass and trophic efficiency in the open ocean, Nature Communications (February 2014)
- Roland Proud et al., on the uncertainty in mesopelagic biomass estimates, ICES Journal of Marine Science 76(3) (1 May 2019)
- Robert Blasiak et al., Corporate control and global governance of marine genetic resources, Science Advances 4(6) (June 2018)
- Muriel Rabone et al., How many metazoan species live in the world’s largest mineral exploration region?, Current Biology 33(12) (2023)
- Daniel O. B. Jones et al., Long-term impact and biological recovery in a deep-sea mining track, Nature (26 March 2025)
- Andrew Sweetman et al., on oxygen production at the abyssal seafloor, Nature Geoscience (22 July 2024), together with the published rebuttals and the editor’s note of 8 April 2026
- United Nations, the BBNJ Agreement (the High Seas Treaty), in force 17 January 2026
- National Centre for Environment and Energy, Aarhus University, on oxygen depletion in Danish waters (4 October 2024)
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