16 Ocean Creatures That Live in Total Darkness

What life lurks in the deepest, darkest parts of our planet's oceans? These unexplored remote areas hold secrets about animal behavior that humans have never seen. And because there are more questions than answers about life at the bottom of the ocean, our imaginations run wild with tales of sea serpents like the Kraken or the Loch Ness Monster.

But there are otherwordly creatures living thousands of feet below the surface, and they've adapted to their hostile environment over millions of years by taking on some unbelievably cool—and in some cases seriously odd—physical characteristics. Here are 16 rarely-seen denizens of the deep.

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Anglerfish

There are more than 200 species of anglerfish, which live in the dark depths of the Atlantic and Antarctic Oceans as far as a mile below the surface. These carnivores are usually brown or gray and can grow up to 3 feet long, though most are around a foot long.

Anglerfish have giant heads, big mouths, and sharp teeth that make them look like something straight out of a horror film. Only female angler fish have the appendage that tells the story of their name. They have a section of their spine that juts out above their mouth and acts as a fishing pole. The very tip has bioluminescent bacteria that light up when the angler fish wiggles it to attract prey.

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Chambered Nautilus

The home range of the nautilus is generally deep-water marine areas in the Western Pacific, American Samoa, and the coastal Indian Ocean. During the day, the nautilus can be found up to 2,000 feet deep, but the animals move to shallower water at night to feed on hermit crabs and fish. Like octopus and squid, this gorgeous chambered nautilus is a cephalopod, meaning its "feet" (in this case tentacles) are attached to its head. The nautilus has terrible vision, as its primitive eyes have no lenses. Instead, it works like a pinhole camera.

Its protective brown-and-white striped shell has chambered compartments called camerae. The chambers are closed except for the large outermost one: that section contains the animal with up to 90 tentacles. The nautilus fills the 30 or more inner camerae with gas to stay in place or adds liquid to the chambers to dive.

The nautilus first appeared roughly 4.5 billion years ago and has since changed little.

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Whiplash Squid

The whiplash squid hovers at the ocean bottom, as deep as 4,920 feet, in a vertical position. The squid resembles a tuning fork in this stance and uses it to remain in its feeding zone. This creature uses the fins on its mantles to move through the water and hold its hover position. Some have bioluminescent spots called photophores that produce light on the skin or around the eyes.

Scientists know very little about the whiplash squid because, until modern deep-sea submersibles spotted them in 1992, they were only able to examine dead specimens. The ROVs and AUVs of the years beginning in 2011 have brought back much better footage.

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Mariana Hadal Snailfish

translucent pinkish white snailfish on ocean floor — Courtesy of Schmidt Ocean Institute

Mariana hadal snailfish (Pseudoliparis swirei) have been spotted as deep as 26,831 feet, more than 5 miles below the surface, in the Mariana Trench. This habitat, called the hadal zone, lends its name to the fish. These fish may look like cute tadpoles, but they are the top predators in their habitat. Due to their deep-sea home, they have evolved to have thinner muscles, larger stomachs, livers, and eggs, and more flexible cartilage bones than their shallow-water relatives.

Scientists estimate that these fish withstand pressure equivalent to the Eiffel Tower resting on someone's big toe.

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Common Fangtooth

The common fangtooth resides in the dark depths of the ocean—some more than 16,000 feet deep. These fish mostly inhabit tropical and temperate waters, but scientists also have documented them in the subarctic. Despite its ferocious appearance, the fangtooth is relatively small—only about 7 inches. Those teeth are so long, however, that the fish can't close their mouth.

Many things remain a mystery about this fish. Some scientists suggest that the fangtooth is a fierce predator that actively seeks out prey. Others suggest that they, like many deep-sea organisms, prefer an ambush-style of hunting. Oddly enough, they swallow their prey whole and don't use those teeth to chew first.

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Cookiecutter Shark

gloved hands and forefingers holding open the small round mouth of a shark with many triangular sharp pointy teeth — JSUBiology / Flickr / CC by 2.0

The cookiecutter shark prefers warm water and lives in oceans near the equator at depths of 1,000 feet. This stuff-of-nightmares mouth takes circular cookie-shaped chunks of flesh from its victims. A horrifying visual, yes, but these sharks are parasites, which means they harm—but do not kill—other fish or marine mammals.

As far as sharks go, these are on the petite side, measuring up to 19 inches.

Previously, cookiecutter sharks had the common name of cigar sharks for two reasons: First, their bodies are long and cylindrical like a cigar, and second, they have a dark collar around their gills that looks like the band on a cigar. They also have bioluminescent light organs that make them appear dark from above and light from below. Researchers think that the dark bar, combined with the illuminated main body, tricks prey into thinking a small fish is above them.

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Viperfish

brown and cream colored fish with prominent round eye that seems to glow, large mouth with many long, translucent pointy teeth — Francesco Costa / Wikimedia Commons / CC BY SA 3.0

The unlovely viperfish haunts the tropical and temperate ocean at depths of up to 9,000 feet. It generally lives about 5,000 feet below the surface during the day. At night, it ascends to shallower water to hunt. This predator is another deep-sea fish with an outsized mouth, a giant lower jaw, and fang-like teeth. Like the angler fish, viperfish have light-producing organs that they dangle near their bodies to attract prey. And if that lure doesn't work, these fast swimmers rush their victims and impale them on teeth so long they don't fit in their mouth.

This foot-long fish comes in a variety of colors, from green to silver to black to blue.

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Frilled Shark

Deep-Sea Fish, Frill Shark Found Alive In Numazu, Japan — Awashima Marine Park / Getty Images

Frilled sharks are another deep-sea dweller that is rarely seen because they most often live about 1,600 to 3,280 feet underwater. They might even be the source of sea monster stories with their eel-like bodies, as they have about 300 triangular teeth arranged in 25 rows. The frilled shark grows as much as 5 or 6 feet long. Interestingly, no one has ever seen a frilled shark eat.

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Lanternfish

Minnow like fish with spiny top fin and big round eye — NOAA's Fisheries Collection / SEFSC Pascagoula Laboratory; Collection of Brandi Noble, NOAA/NMFS/SEFSC / Wikimedia Commons / Public Domain

Lanternfish bring their own light to their habitat 1,300 to 3,000 feet below the surface during the day. At night, they ascend to feed as high up as just 82 feet below the sea level. The lanternfish uses photophores on its body and snout to provide the light to see with its large eyes.

These tiny swimmers are only 1 to 6 inches long and live about 1,000 feet deep in waters worldwide. Lanternfish are an essential part of the food chain, serving as the primary food source to larger animals like squid, tuna, salmon, whales, and penguins. Unfortunately, lanternfish consume plastic debris from the ocean that then becomes food for other animals.

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Giant Spider Crab

The giant spider crab is found 500 to 1,000 feet underwater in Suruga Bay off the coast of Japan, where people consider them a delicacy. Each year, tens of thousands of them migrate to Port Phillip Bay in Australia. The largest known crab species, the giant spider crab, can have a leg span of 12 feet, a body 16 inches across, and can weigh around 40 pounds.

These massive crustaceans can live to be 100 years old and will eat just about anything. But they're also prey for even bigger animals such as squid. To protect themselves when young, they sometimes decorate their often orange-and-white shells with kelp and sea sponges to better blend into the ocean floor.

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Northern Wolffish

fish that looks like a stone except for the large, white, open mouth — Derek Keats / Wikimedia Commons / CC BY 2.0

Northern Wolffish prefer the cold depths of the North Atlantic, residing anywhere from 328 to 5,577 feet below sea level. There is a unique compound in their blood that acts as an antifreeze in the icy waters. Atlantic wolffish are voracious predators with eel-like bodies, large teeth, big heads, and powerful jaws to eat hard-bodied prey such as sea urchins, crabs, and snails. Like eels, they favor rocky ocean bottoms and seaweed beds where they can hide.

These solitary fish grow up to 5 feet long and can weigh as much as 40 pounds. While the wolffish pictured here is blue, they also may be a purplish-brown or dull olive green.

If, by any chance, you see one or manage to reel one in while fishing, watch out because their bite can be painful.

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Bluntnose Sixgill Shark

The migratory bluntnose sixgill shark is found worldwide at depths to 6,500 feet, though it will move to shallower water to feed. These bottom-dwelling sharks have powerful bodies, broad heads, and fluorescent, blue-green eyes. Sixgill sharks range in color from gray to tan to black on their backs, but they're all lighter underneath. And they're big. The Shark Research Institute reports they grow to almost 16 feet long.

It takes a lot of food to fuel that body. Their prey is dolphinfish, billfish, flounder, cod, hagfish, lampreys, chimeras, rays, dogfish, and prickly sharks.

One fascinating adaptation this shark has to help it live in the dark depths is a huge pineal window, a large, light-colored spot between its eyes that allows seven times more light to enter its brain.

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Giant Tube Worms

Communities of giant tube worms form over a mile underwater in the Pacific Ocean around hydrothermal vents. These fissures on the ocean floor spout scalding, acidic water, and poisonous gas. But even in that dark, hostile environment, the swaying white tubes can grow up to 8 feet tall at a rate of up to 33 inches a year.

They have no mouth or digestive system; instead, they survive via a symbiotic relationship with the bacteria living inside them. And true to their name, they are the heaviest known worms in the world.

Scientists first discovered giant tube worms in 1977 off the coast of the Galapagos Islands in the Galapagos Rift, roughly 8,000 feet below the surface.

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Oarfish

long flat serpent like creature with many short hair like fins along the edge laying washed up on beach — Katia Cao / Fishbase / CC BY 3.0

These elongated fish live at depths of 656 feet, but some live as far down as 3,280 feet. Oarfish are said to have inspired tales of "sea serpents" through the years. Looking at pictures of oarfish that wash up on beaches, it's easy to see why. The world's longest bony fish can grow up to 56 feet long and weigh 600 pounds.

Found all over the world, these fish aren't sought for their gelatinous meat, though some people trophy hunt for them. Instead of scales, they have tubercles covered in a material called guanine. When they come to the surface, their skin becomes soft and is easily damaged.

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Squat Lobsters

white animal that looks like a hermit crab out of its shell, a galatheid squat lobster, on a field of dark black and grey pillow basalt — NOAA Okeanos Explorer Program, MCR Expedition 2011 / Public Domain

Squat lobsters, which are neither lobster nor crab, live on the seafloor at depths of up to up to 8,579 feet. They are most closely related to hermit crabs. Squat lobsters are often blind and usually soft, and they don't carry shells on their backs. Instead, they squeeze into crevices, many times in deep-sea coral, to protect their body and leave their claws exposed.

These scavengers grow to just a few inches long, though their arms can be several times their body length. Squat lobsters scavenge some unlikely meals, such as the wood-based diet of the Munidopsis andamanica. That species eats dead tree falls and wooden shipwrecks. Whalebones and turtle shells make up the diet of other species.

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Dinner Plate Jellyfish

close up of Solmissus jellyfish with 26 thin tentacles extending out from the belly in dark blue water — NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts / Public Domain

This dinner plate jelly is one of the jellyfish that calls the dark of the sea home, in this case, 2,300–3,300 feet below the surface. Unexpectedly, they don't wait around for food, choosing instead to actively seek out the zooplankton and other jellyfish that it eats. This behavior is unique among cnidarians. The Okeanos Explorer photographed the one above in the Musicians Sea Mounts, a set of underwater mountains north of the main Hawaiian Islands. Before this exploration, the area had not received much attention from scientists. It documented many types and aspects of marine life, including other little known and previously undiscovered jellyfish, for the first time.