Less than 5% of the ocean has been mapped in detail. The rest is dark, cold, and inhabited. Scroll down, because we're going in.
The top 200 metres. Photosynthesis happens here, which means food. Almost every ocean creature you can name lives in this thin band. Below it, everything changes, and most of what we'll meet has never been photographed alive.
The largest predatory fish on Earth. They can detect a single drop of blood in 100 litres of seawater and sense the electrical fields of prey through gel-filled pores in their snouts called the ampullae of Lorenzini. Most attacks on humans are believed to be exploratory bites, since they don't actually like the taste.
Warm-blooded, which most fish aren't. They cross the Atlantic in 60 days and can sprint at 70 km/h. Their meat is in such demand that a single fish sold for $3.1 million at Tokyo's Toyosu market in 2019. Strict quotas have begun bringing the population back from collapse.
Three hearts. Blue blood. Nine brains, eight of them distributed across its arms. They can change colour and texture in a third of a second, taste with their suckers, and solve puzzles that other invertebrates can't. They live four years and die after mating.
The largest fish alive on Earth, bigger than a school bus. Despite the size and the shark name, they eat almost exclusively plankton, filtering thousands of litres of water an hour through their gills. The spot patterns on their backs are unique to each individual, like fingerprints. They can live more than 100 years.
Not actually whales. They're the largest member of the dolphin family. Different pods around the world hunt entirely different prey: fish, seals, sharks, even other whales. Each pod has its own dialect of vocalizations that calves learn from their mothers. They're one of the only animals besides humans known to undergo menopause; post-reproductive females become the wisdom-keepers of the pod.
The largest turtle on Earth, and the only one without a hard shell. Its carapace is made of leathery skin reinforced with seven longitudinal ridges. They dive deeper than any other reptile, regularly hunting jellyfish at 1,200 metres. Their throats are lined with backward-pointing spines that trap soft prey. Critically endangered, in part because they mistake plastic bags for jellyfish.
The heaviest bony fish on Earth, up to 2,300 kg. They look like a fish that's been chopped in half: a giant disc with no proper tail. They sunbathe at the surface, lying flat on their sides, supposedly so seabirds can pick parasites off them. They lay more eggs than any other vertebrate (300 million at a time), of which almost none survive.
And we're only at the bottom of the sunlight zone. From here, every metre down is darker than the last. The next stop is twilight, and most of life on Earth is heading there with you.
Only blue wavelengths penetrate this deep. Red becomes invisible, which is why so many creatures here are red, the colour of camouflage. 90% of all fish biomass on Earth lives in this band, mostly in a layer that migrates upward every night to feed in the dark.
Its head is transparent. The green spheres inside aren't eyes you can see. Those are the lenses. The actual eyes are tubular and rotate inside the clear dome to look straight up through its own forehead, watching for the silhouettes of prey above. Nothing else on Earth has eyes like this.
Its full name translates to "vampire squid from hell." It's neither, but rather a living fossil from a branch of cephalopods 300 million years old. It doesn't hunt. It drifts through the oxygen-minimum zone eating "marine snow," the dead plankton and fecal pellets drifting from above. When threatened, it inverts its webbed cape over itself like an umbrella of soft spines.
The largest toothed predator on Earth. They dive to 2,000 metres to hunt giant squid in total darkness, holding their breath for 90 minutes. Their clicks are the loudest sound made by any animal, reaching 230 decibels, which would rupture human eardrums. They communicate in family-specific dialects called "codas."
The model for centuries of kraken legends. We had never seen one alive in its habitat until 2004, when a Japanese team photographed one. The first live video came in 2012. Their eyes are the largest of any animal, roughly basketball-sized, likely evolved to detect the faint glow of approaching sperm whales, their main predator.
By sheer biomass, this is probably the most numerous vertebrate on Earth, an estimated 550 to 660 million tonnes of them, more than all the cattle and humans combined. Every night, they migrate upward by hundreds of metres to feed near the surface, then sink back down at dawn. It's the largest daily animal migration on the planet, and you've probably never heard of it.
Mostly mouth and stomach. The jaw alone is a quarter of its body length and unhinges to engulf prey larger than itself, and the stomach stretches to match. At the tip of its long whip-tail, a pink bioluminescent organ lures curious smaller fish straight into the mouth. They live alone, in the dark, eating whatever drifts close enough.
One of the only animals on Earth that produces red light, and one of the only deep-sea creatures that can see it. Since red is invisible to most predators and prey down here, the dragonfish uses its red beam like a sniper's infrared scope: it can see everything, and nothing can see what it's seeing. The chin barbel lures curious fish with a separate green-blue glow.
Deep red, the colour of camouflage in dark water. Their stomachs glow red after a meal because the bioluminescent prey they've eaten is still flashing, so they evolved to keep that light hidden inside opaque red flesh. Otherwise the snack would alert every predator in the vicinity. They live for up to 30 years in deep, cold fjords.
The tallest building ever built, 828 metres from base to spire. If you flipped it upside-down here, the antenna tip would only just reach down to where you are now. And we're still hundreds of metres above the midnight zone.
No light from above reaches here. Ever. The only light is what the creatures themselves make. Bioluminescence becomes the dominant currency of life. Pressure exceeds 100 atmospheres. Temperatures hover near freezing. This is the largest habitat on Earth.
The lure on her forehead glows with bioluminescent bacteria. She is "she" because males are 40 times smaller. When a male finds a female (rare, in the dark), he bites her side and fuses to her body, dissolving into a permanent sperm-producing appendage. A female may carry several fused males at once.
The deepest-living octopus, found down to 7,000 metres. The "ears" are fins it uses to swim, drifting slowly and gently through total darkness. Unlike its shallow cousins, it can't squirt ink (no predators chase it down here), and it swallows prey whole. Often considered one of the most peaceful creatures in the abyss.
The longest-lived vertebrate on Earth. Carbon dating of eye lenses suggests they live 250–500 years, reaching sexual maturity at around 150. They cruise just above the seafloor at less than 1 km/h. Almost all of them carry a parasite that destroys their corneas, leaving them nearly blind, which doesn't seem to matter down here.
The most famous shipwreck on Earth. Struck an iceberg on 14 April 1912, sank in under three hours, killed roughly 1,500 people. Lay undiscovered for 73 years until Robert Ballard and Jean-Louis Michel located it on 1 September 1985 using the Argo submersible. The hull is being slowly devoured by iron-eating bacteria called Halomonas titanicae, and most scientists estimate it will collapse entirely within the next 30 years.
A relic from 125 million years ago, the only surviving member of an ancient shark family. Its jaws are loosely attached to its skull on stretchy ligaments. When it spots prey, the entire mouth shoots forward like a slingshot, faster than any other shark known. The pink colour you can see is its blood vessels through translucent skin.
Holds the record for the largest teeth in proportion to body size of any fish in the ocean. The lower fangs are so long that the fish has evolved special pockets in the roof of its mouth. When it closes its jaw, the bottom teeth slide into sockets in its skull, on either side of its brain. Otherwise its mouth wouldn't shut.
Tiny but terrifying. It uses suction-cup lips to clamp onto larger animals, then rotates its body 360° to cut out a perfectly circular plug of flesh, like a cookie cutter. Tuna, whales, dolphins, sharks, and even submarines have been found with these crater-shaped wounds. The exposed "collar" on its belly mimics a small fish silhouette to lure predators close enough to bite.
Named for their thin axe-blade silhouette. Their tubular eyes point straight up, watching for the silhouettes of prey above against the faint glow from the surface. Their bellies are lined with photophores that emit a soft blue light exactly matching the brightness of the water above, a trick called counter-illumination that erases their own shadow from below.
The wreck sits at 3,810 metres. Stack every super-tall skyscraper ever built end-to-end, and you still haven't reached the seafloor here. The water above you weighs as much as a small mountain.
Beyond the continental shelf, endless plains of fine sediment stretch across most of the seafloor. Pressure: 400 atmospheres. Temperature: 2°C. Food is so scarce that creatures here have evolved to eat almost nothing and move almost not at all. Most species we find down here are new to science.
Famous for looking miserable, but only on the surface. At depth, the pressure holds its gelatinous body in a normal fish shape. Brought up, its tissues expand and droop. It lives near 1,200 m, mostly motionless, mouth open, waiting for crustaceans to drift past. It barely has muscles. It doesn't need them.
Almost entirely transparent. Only the eyes, optic nerve, and digestive tract are visible. Everything else is glass. Camouflage by negation: predators looking up see only the faint silhouette of organs against the sky of black water above. Filmed alive on camera fewer than a dozen times.
Its anatomy hasn't changed much in 80 million years, a swimming relic of the late Cretaceous, when sharks looked more like eels. Three hundred trident-shaped teeth arranged in 25 rows. Pregnancies last three and a half years, the longest of any vertebrate on Earth. Almost never seen at the surface; when one is, something is usually wrong with it.
The submarine that revealed the deep ocean to humanity. Commissioned in 1964, it has made more than 5,000 dives. It dove on Titanic in 1986 with Robert Ballard. It found and documented the first hydrothermal vents in 1977, a discovery that rewrote biology, because chemosynthetic life forms can exist without sunlight. Alvin's pressure sphere is made of two-inch titanium.
First described in 1873 from a single dead specimen, then not seen again for 144 years. Australia's RV Investigator rediscovered them off Sydney in 2017 at 4,000 metres. Eyes are vestigial. The nostrils sit underneath the head, and the mouth too. From above, there is nothing resembling a face at all. Hence the name.
A pill bug the size of a house cat. Closely related to the roly-poly bugs in your garden, but scaled up by a factor of fifty. They scavenge whale carcasses on the abyssal plain. In captivity, one famously refused to eat for five years and survived. They curl into a ball when threatened, just like their tiny terrestrial cousins.
Sea cucumbers that have evolved tube feet to walk along the seafloor, and they really do look like tiny translucent pigs. They scavenge organic matter that drifts down ("marine snow"), and travel in herds across the abyssal mud. A surprising fact: each sea pig is often home to a tiny shrimp or king crab living between its legs, hiding from predators.
The pride of the German Kriegsmarine. Sunk in a Royal Navy pursuit on 27 May 1941 after just nine days of operation, taking over 2,000 of her crew down with her. The wreck was located in 1989 by Robert Ballard (the same man who found Titanic). It sits remarkably intact on the abyssal plain, almost a kilometre below where Titanic rests, in nearly preserved condition because the cold and pressure slow corrosion at this depth.
Kilimanjaro rises 5,895 metres from sea level. From where you are now, you could look up at its summit, and still have most of the world's tallest peaks looming above. We've left the abyss. Next stop: the trenches.
Only in the ocean's trenches. Pressure can exceed 1,000 atmospheres, equivalent to fifty 747s stacked on your fingertip. We've sent more people to the moon than to the bottom of the Mariana Trench. The creatures here are some of the most alien on this planet.
The deepest-living fish ever filmed, captured on camera at 8,178 metres. Its body is mostly water and gelatinous flesh, with thin transparent skin and no scales. Its bones are partly cartilage. Its skull has a hole at the top to let pressure equalise. Bring it to the surface, and it dissolves.
Most amphipods are the size of a grain of rice. This one is the size of a small cat, a freakishly enlarged crustacean that scavenges trench floors. They've been pulled up in baited traps from over 7,000 metres. Why they grow so large at this depth, where food is scarcest, is still a mystery to biologists.
The first human descent to Challenger Deep. Walsh and Piccard reached 10,912 metres, the deepest anyone had ever been. The trip down took five hours. They spent only twenty minutes on the bottom before a cracked viewport forced them to ascend. For 52 years, no human returned. Piccard's father Auguste designed the vessel; his son Bertrand later circumnavigated the world in a solar plane.
The filmmaker spent seven years and around $10 million building a submersible to descend solo. On 26 March 2012, he piloted Deepsea Challenger to 10,908 metres, becoming the third person in history to reach the bottom of the Mariana Trench, and the first to do it alone. He spent nearly three hours on the seafloor collecting samples. The descent took 2 hours, 36 minutes. Ascent took 70.
Currently the deepest-diving manned submersible ever built. Vescovo took it to 10,925 metres in the Mariana Trench's Challenger Deep, a record that beats Cameron's by 17 metres. Unlike previous attempts, Limiting Factor is rated for repeated dives to full ocean depth. It has now made more than two dozen descents to the deepest five trenches on Earth.
Everest stands 8,848 metres from sea level. The ocean here is deeper than the tallest mountain on Earth is tall. If you took the entire peak, base, snow, the route through the Khumbu Icefall, all of it, and submerged it from where the seafloor of the trench begins, the summit would be drowned under a kilometre of water.
Found only in trenches. To survive the pressure, and the corrosive seawater that breaks down most calcium-based shells, it secretes an aluminium-based gel that hardens around its body when it contacts seawater, forming a kind of bio-armor. Recovered from the Mariana Trench, Japan Trench, and the Kermadec Trench. The discovery of metallic biology this far down has implications for medicine and materials science.
The deepest shipwreck ever found. A US Navy destroyer sunk at the Battle off Samar on 25 October 1944, after a heroic suicide-charge against a vastly larger Japanese force. Lost for 75 years. Finally located in 2019 and definitively confirmed in 2021 by Victor Vescovo aboard Limiting Factor. Only 186 of 327 crew survived the battle. The wreck sits on a steep slope in the Philippine Trench.
"Ghost shark" is not actually a shark, but from a lineage that split from shark ancestors 400 million years ago. They have a venomous dorsal spine and ratlike incisor teeth that grow continuously. Males have a club-like appendage on their forehead, used to grip females during mating. Their large green eyes shine in submersible lights like a cat's. Many species were unknown to science until the last twenty years.
A sponge that builds its body from pure silica, actual glass, in a lattice so structurally elegant that materials scientists studied it as inspiration for fibre optics. Inside almost every adult, a male and female shrimp grow up together, get too large to leave the openings, and live out their lives as a pair. In Japan the sponge skeletons are traditional wedding gifts: "till death do us part."
You're at the deepest known point on Earth. The water above you weighs 1,100 atmospheres, like having fifty fully-loaded 747 jumbo jets pressing down on every square inch of your body. More humans have walked on the Moon than have come this far. We've sent only twenty-three.
↓ scroll through the full descent below ↓
Every deep-sea expedition discovers species nobody has ever seen. The ocean is the last great unmapped wilderness on Earth. There's still time to learn it, and to protect it before we lose what we haven't met yet.