10 Deep Sea Creatures That Are (Almost) Too Bizarre to Be Real

The pelican eel (Eurypharynx pelecanoides) is a type of gulper eel that uses its large, pelican-like mouth to gulp up its prey. Like other members of the Eurypharyngidae family, the pelican eel's mouth is about a quarter length of its tapered body, which can expand to fit the prey it swallows whole.

Pelican eels live in the mesopelagic zone (also known as the middle pelagic or twilight zone), at depths of 9,000 feet (2,700 meters) and more along with other terrifying-looking deep-sea creatures like the vampire squid.

The common fangtooth (Anoplogaster cornuta) is a rarely spotted deep-sea fish that the Monterey Bay Aquarium Research Institute (MBARI) calls "almost as elusive as it is astonishing."

It gets its name from the two long sharp teeth that protrude from its upper jaw. According to the Smithsonian Institution, the fangtooth's teeth are the largest of any sea creature, relative to its body size of up to 7 inches (18 centimeters). They also have two long fangs that come out of its lower jaw.

The fangtooth fish hunts small crustaceans, cephalopods and other deep-sea fishes by opening its mouth and sucking in, like a deep-sea vacuum. "They seem to eat anything that will fit in their mouths," Tracey Sutton, a professor with the Guy Harvey Oceanographic Center at Nova Southeastern University in Florida, told Newsweek.

Fangtooth fish primarily live in the mesopelagic (twilight) and bathypelagic (midnight) zones at depths of 1,650 to 7,000 feet (500 to 2,100 meters) but have been spotted as deep as 16,000 feet (almost 5,000 meters).

With a leg span of up to 12 feet (3.8 meters), the Japanese spider crab (Macrocheira kaempferi) is the biggest crab in the world. It lives in the Pacific Ocean's mesopelagic (twilight) zone at depths from 660 to 1,800 feet (200 to 550 meters).

The Japanese spider crab has 10 legs, eight of which it uses for walking. The other two legs have claws and are for pinching. The deep sea creature spends its days walking along the sea floor, scavenging for dead animals and plants.

Some deep-sea creatures are rarely seen by humans because they stay close to the ocean floor. Sea cucumbers (class Holothuroidea), however, can survive in both shallow waters and the deep ocean. For food, they typically use their tube feet to gather tiny bits of algae and decaying organisms on the sea floor.

Sea cucumbers are part of the echinoderm family, which includes sea stars, sea urchins and crinoids. The smallest species of sea cucumber — there are over 1,200 — is the Psammothuria ganapati, which is about 0.16 inches (4 millimeters) long. The largest is the Synapta maculata, also known as the snake sea cucumber, which can grow up to 10 feet (3 meters) long, according to the Natural History Museum.

Although it's in the same class (Chondrichthyes) as a great white shark, the 7-foot (2-meter) frilled shark (Chlamydoselachus anguineus) looks more like an eel. "The head on it was like something out of a horror movie," fisherman David Guillot, who accidentally caught a frilled shark in 2015, told 3AW radio.

This 80-million-year-old deep-sea dweller ranges from the pelagic to the benthic zones, with an upper limit of 164 feet (50 meters) below sea level and a lower limit of around 5,000 feet (1,500 meters) deep.

According to the Shark Research Institute, it may swim with its mouth open, using its "conspicuously white teeth" to attract prey before swallowing them whole.

The giant isopod (Bathynomus) is a deep-sea crustacean related to roly-polys and pill bugs. Although the "giant" isopod ranges in size from 3 to 20 inches (8 to 51 centimeters) long, it dwarfs the majority of marine isopods, which could be as small as 0.01 inches (0.3 millimeters).

The giant isopod is a prime example of deep-sea gigantism, a phenomenon seen in other deep-sea creatures like the giant squid and the Japanese spider crab. It lives from 550 to 7,020 feet (170 to 2,140 meters) deep.

"As far as we know, they are primarily scavengers," Ruth Carmichael, senior marine scientist at the Dauphin Island Sea Lab and professor of marine and environmental sciences at the University of South Alabama, told HowStuffWorks. "They play an important role in nutrient and element recycling" by digesting bits of decaying fish, crustaceans and sea sponges on the sea floor.

Like a daddy longlegs, the giant sea spider (Colossendeis) has long, delicate legs extending from a smaller body. Unlike a daddy longlegs, the giant sea spider prefers to live at the bottom of the ocean rather than in the corners of your ceiling.

Some species of sea spiders are tiny — the smallest have legs only 0.03 inches (1 millimeter) long — but the giant sea spider, which lives at depths of 7,200 to 13,100 feet (2,200 to 4,000 meters), can be up to 20 inches (51 centimeters) long.

Sea pigs (Scotoplanes) are some of the weirder-looking deep-sea animals. They are not related to pigs — the name comes from their pinkish transparent bodies and stubby tube legs — but are instead a type of sea cucumber. Their other resemblance to pigs is that they will eat almost anything.

According to MBARI, they reach lengths of up to 6.4 inches (17 centimeters) and live at depths of 3,300 to 19,500 feet (1,000 to 6,000 meters). Their habitat is the seafloor of abyssal plains, and they eat decomposing organic material.

Anglerfish (sometimes spelled as "angler fish") refers to around 200 deep-sea fish species found at various depths — up to 16,400 feet (5,000 meters) — and in many sizes — from 0.25 inches (6.2 millimeters) to 4 feet (1.2 meters) long.

They are divided into four groups: batfish, goosefish, frogfish and deep-sea angler.

"New ones [species] are still coming up," Ted Pietsch, a professor at the School of Aquatic and Fishery Sciences at the University of Washington and author of "Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea," told HowStuffWorks. "They live so deep that we don't really have a good idea of how big they actually get. We send nets down to collect them, and the deeper we go the larger specimens come up."

Anglerfish attract bioluminescent bacteria to a light-up lure at the end of a dorsal appendage, which attracts prey. The females of the species do all the hunting. Females are much larger than males — up to 60 times larger — and provide nutrients to their male mates.

In place of the foot found underneath the shell of a regular ole land snail, the sea angel (clade Gymnosomata) has two wings it uses to propel itself through the ocean.

The Monterey Bay Aquarium calls the sea angel "a type of swimming snail," but without a shell. Their transparent bodies are exposed — hence the name Gymnosomata, or "naked body."

Sea angels prey on other swimming snails, such as sea butterflies, using a tentacle-like appendage to scoop the flesh out of the shell. Despite their predatory habits, sea angels are small: just 0.4 to 0.78 inches (1 to 2 centimeters) long. They can be found from the surface to 5,921 feet (1,805 meters) deep.