How Deep Do Krill Go? From Surface Swarms to 3,000 Metres Down

Most Antarctic krill live in the upper ocean. Echo sounder surveys and net samples have long shown adults concentrated in the top 150 metres or so, often in the top 100, rising towards the surface at night. But krill can go much deeper. In 2008 scientists reported adult Antarctic krill feeding just above the seabed at 3,000 metres, and a study published in September 2026 found egg-bearing females at a hydrothermal vent more than 900 metres down.

So the short answer to "how deep do krill go?" is: usually not far, sometimes astonishingly far. The deepest well documented sighting of adult Antarctic krill is around 3,000 metres. In our game Krillion, a krill on a perfect dive goes more than twice as deep as that, which we will come back to at the end.

Antarctic krill, Euphausia superba, are shrimp-like crustaceans that grow to about 6 centimetres and live for several years. They live all round Antarctica in the Southern Ocean, most densely in the Atlantic sector around the Antarctic Peninsula and the Scotia Sea. Their food, mostly phytoplankton, grows where there is light, so that is where they spend most of their time: in the sunlit layer, and, for young krill especially, under the winter sea ice, where they graze algae off its underside.

That habit shaped how krill were studied. Ships sample with nets and acoustic surveys that concentrate on the upper few hundred metres, and as the krill researcher Kim Bernard has pointed out, scientists have largely studied krill in the upper 300 metres of the ocean. What happens deeper has been, until recently, mostly guesswork.

Antarctic krill are only one of about 85 krill species, and a few others are true deep sea animals. Bentheuphausia amblyops, known simply as the deep sea krill, lives below about 1,000 metres and is thought to be the most primitive krill alive. When people ask how deep krill go, though, they almost always mean the Antarctic species, the one whales eat, so that is the one this article follows.

Many krill do not hold a single depth. They move up and down on a daily cycle called diel vertical migration. The classic pattern is to rise towards the surface at night, when it is safer to feed on phytoplankton in the dark, and sink deeper during the day, away from the eyes of penguins, seals, fish and seabirds that hunt by sight.

For Antarctic krill the pattern is real but flexible. Studies have found migrations from the mixed surface layer down to around 100 metres, and the behaviour changes with season, age and conditions. Larvae make some of the most pronounced daily migrations. Adults sometimes migrate, sometimes stay near the surface day and night, and seem to weigh food against danger as the balance shifts. One study in the Scotia Sea found krill tended to sit deeper in winter and shallower in summer.

Diel vertical migration is not a krill oddity. Across the world's oceans, countless small animals make the same commute every night, which many scientists describe as the largest daily migration of animals on Earth.

The idea that krill were an upper ocean animal was shaken by a short paper in Current Biology in February 2008, by Andrew Clarke of the British Antarctic Survey and Paul Tyler of the National Oceanography Centre, Southampton. It came from the first science dives of the UK's deep diving remotely operated vehicle Isis, during the 2006 to 2007 Antarctic summer, which filmed the seabed of Marguerite Bay off the western Antarctic Peninsula from 200 metres on the continental shelf down to 3,500 metres on the abyssal plain.

At 3,000 metres the cameras found adult Antarctic krill just above the seabed, actively feeding. On the bottom was a layer of phytoplankton that had sunk from the surface and was still green, and the krill were eating it. Some of the females appeared ready to spawn. Clarke suggested that krill visit the deep sea floor to feed on the algae that rains down at the end of the summer.

The British Antarctic Survey called it a discovery that completely changed scientists' understanding of the animal, though the researchers were careful to say it did not mean krill stocks were much bigger than thought. A follow-up study by Katrin Schmidt and colleagues in 2011 found that krill feeding on the seabed is not a rare quirk but happens around Antarctica, all year round.

The newest surprise came in September 2026, in a paper in Communications Biology led by the biological oceanographer Kim Bernard. During an expedition in late December 2024 aboard the Schmidt Ocean Institute's research vessel Falkor (too), the team used the remotely operated vehicle SuBastian to sample a hydrothermal vent site at Hook Ridge in the Bransfield Strait, off the Antarctic Peninsula, more than 900 metres below the surface.

Every krill they collected from the vent was a female heavy with eggs. Their gut microbes, stable isotopes and trace metals all pointed to the same story: they had been eating chemosynthetic microbes, the kind that live off chemicals from the vent rather than sunlight. They also carried raised levels of manganese, zinc and iron, metals important for producing eggs. Video from a second vent field, Quest Caldera, showed that the behaviour was not a one-off.

Bernard called the finding shocking. Krill have long been assumed to spawn in the upper ocean, so finding reproductive females at a deep vent raises the possibility that vents are part of their breeding life, and that some critical habitat for the species lies far below where fishing rules and surveys have looked.

For whales and everything else. Antarctic krill sit near the centre of the Southern Ocean food web. Penguins, seals, fish, squid, seabirds and baleen whales eat them directly or eat something that does. A 2021 study in Nature led by Matthew Savoca estimated that before industrial whaling, baleen whales in the Southern Ocean ate around 430 million tonnes of krill a year. Where krill are, and at what depth, decides who can reach them.

For counting them. Krill stocks are estimated mostly from surveys of the upper ocean. If a share of the population spends time near the seabed or at vents, those surveys may miss them. That matters because the krill fishery's catch limits rest on those estimates.

For the climate. Krill are part of the ocean's biological carbon pump. They eat carbon-rich phytoplankton near the surface and produce dense faecal pellets that sink quickly. A 2024 study in Nature Communications by Emma Cavan and colleagues estimated that Antarctic krill pellets lock away about 20 million tonnes of carbon each productive season, comparable to what the world's mangroves, salt marshes and seagrass meadows store. Pellets only need to sink a few hundred metres, 381 metres on average in that study, to keep their carbon out of the atmosphere for a century or more. Krill that move up and down through the water column help move that carbon down.

• Size: up to about 6 centimetres long and 2 grams.
• Numbers: a 2009 study by Angus Atkinson and colleagues estimated about 800 trillion animals, weighing around 379 million tonnes.
• Swarms: densities of 10,000 to 30,000 krill per cubic metre are often quoted, though surveys usually measure far fewer.
• Usual depth: mostly the top 150 metres, rising towards the surface at night.
• Deepest adults filmed: about 3,000 metres, on the seabed off the Antarctic Peninsula.
• Eggs: females release thousands of eggs at a time, which sink before hatching. Over deep water they may sink as far as 2,000 to 3,000 metres, and the larvae then swim all the way back up to the light.

In the Krillion game, depth is your score. You give the rarest correct answer you can to each prompt, and every point sinks your krill 10 metres. A classic dive is seven prompts, and the top tier, One in a Krillion, is worth 100 points, so a perfect dive of 700 points takes your krill to 7,000 metres. That is more than twice the depth of the deepest adult Antarctic krill ever filmed, and deeper than any Antarctic krill has ever been seen.

The water on the way follows the real sea: sunlit shallows and kelp, the twilight zone where daylight runs out, anglerfish territory, the wreck of the Titanic at about 3,800 metres, hydrothermal vents, and on into the hadal zone. Endless mode keeps going past the real ocean altogether, into invented places like a glass orchard and a drowned skyline, all the way to a shrine at 250 kilometres.

Real krill reach the abyss by chasing food that sinks. Yours gets there by finding the answers nobody else thinks of. Krillion Unlimited is free in your browser with no sign up and no daily limit, so you can dive as often as you like and see how far past 3,000 metres you can get.

Clarke, A. and Tyler, P. A., Adult Antarctic Krill Feeding at Abyssal Depths (Current Biology, 2008).

British Antarctic Survey, Krill discovered living in the Antarctic abyss (2008).

Schmidt, K. et al., Seabed foraging by Antarctic krill (Limnology and Oceanography, 2011).

Bernard, K. et al., Antarctic krill at hydrothermal vents in the Bransfield Strait (Communications Biology, 2026).

Cavan, E. L. et al., Antarctic krill sequester similar amounts of carbon to key coastal blue carbon habitats (Nature Communications, 2024).