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13 of the Weirdest Deep Sea Creatures

The Earth's briny waters are full of life—some of it is truly strange and mysterious-looking.

Giant Isopod up closee_rik/Shutterstock

Giant isopod (Bathynomus giganteus)

About 5,000 species of crustaceans in the order Isopoda live in Earth’s oceans. According to the National Oceanic and Atmospheric Administration (NOAA), they all have two pairs of antennae, compound eyes, and four sets of jaws. Their seven-segmented bodies have seven sets of legs for walking, and their six-segmented abdomens have more legs for swimming and breathing. This massive, 2-1/2 foot species—one of nine in the genus Bathonymus—lives in cold waters over 8,000 feet deep in the Pacific and Atlantic, and it can scavenge dead whales, fish, and squid. The Giant isopod is in good company, from other unbelievable underwater species to an underwater graveyard, the 13 creepiest things you can find at the bottom of the ocean give this crustacean a run for its money.

Leafy sea dragon photographed in Indonesia, 2009Kjersti Joergensen/Shutterstock

Leafy sea dragon (Phycodurus eques)

With a multitude of yellowish or greenish appendages that allow it to camouflage itself as seaweed, this 14-inch deep sea creature, closely related to sea horses and pipefish, makes its home in the waters off south and east Australia, according to National Geographic. They eat tiny crustaceans called sea lice and—as with sea horses—designate the males of the species to incubate eggs.

A beautiful NautilusHQ365/Shutterstock

Chambered nautilus (Nautilus pompilius)

These ancient, eight-armed cephalopods that are endangered in their home habitats in the Indo-Pacific, have existed in the deep seas of our planet for 500 million years. Their shells contain chambers that are filled with air for buoyancy—except for the last and largest of them, which contains the animal itself. Nautilus tentacles called cirri allow them to pry the dead animals they scavenge from the seafloor from their shells. They lay the largest eggs (5 cm) in the invertebrate kingdom, which take a year to hatch. They’re only one of infinite numbers of amazing sights in the world’s oceans.

Giant Pacific octopuspr2is/Shutterstock

Giant Pacific octopus (Enteroctopus dofleini)

A solitary, foraging predator of the ocean around Japan, Alaska, and California, this is the biggest octopus of all; the largest recorded weighed 600 pounds and measured 30 feet, according to Oceana. The deep sea creature can change its color to blend with its surroundings, and a squirt of its ink is deadly to other octopuses that threaten it. It can puncture its prey (lobsters, small sharks) with its beak during the four to five years of its life. Like other octopus species, this one has three hearts and nine brains. Here are 23 more of the biggest animals in the world.

Congiopodidae, commonly known as pigfishes, horse-fishes and racehorses.Anky/Shutterstock

Pigfish (Congiopodidae)

Living in up to 2,000 feet of cold water, this family of nine species of long-nosed, scaleless fish is native to the Southern Hemisphere. One species in South Africa is thought to molt its skin like a reptile. Don’t confuse the pigfish with Florida’s hogfish, named for the way it roots around the seafloor with its snout, trying to rustle up prey.

Shaggy Frogfish (Anglerfish)Rich Carey/Shutterstock

Shaggy frogfish (Antennarius hispidus)

Looking like a Muppet but acting like a vicious predator, this denizen of coral reefs can swallow its prey—often as large as itself—whole. Watch this video of a camouflaged frogfish lurking on the ocean floor…before striking fast to gobble any unsuspecting fish that swim near. It has a pom-pom-like lure on its head that beckons all delicious potential meals.

Great Hammerhead shark BahamasHakBak/Shutterstock

Great hammerhead shark (Sphyrna mokarran)

Existing worldwide at depths up to 1,000 feet, this largest species of hammerhead, which grows to about 18 feet long, according to MarineBio, evolved its rectangular-shaped head to maximize its ability to detect its prey through chemical, thermal, and electrical changes. It’s a known cannibal—although it also enjoys a meal of stingray or crab. A female produces a litter of up to 56 pups that hatch inside her body. Like all sharks, hammerheads are greatly misunderstood.

lionfish,sun and oceanstephan kerkhofs/Shutterstock

Lionfish (Pterois volitans and Pterois miles)

Top predator lionfish are hunted by no other deep sea creature and lay as many as 2 million eggs—each—per year. It’s no wonder, then, that these denizens of the Indian Ocean, transplanted via the aquarium trade to Atlantic and Caribbean waters, are taking over, and decimating native species as they go. Their 32 or so bright-colored spines—which scare off would-be snackers—are venomous and can cause everything from sweating to paralysis.

The stargazers are a family, Uranoscopidae, of perciform fishGerald Robert Fischer/Shutterstock

Stargazer fish (Uranoscopidae)

This family of deep-sea Mediterranean and Atlantic fish, about 50 species in all, have mouths, nostrils, and eyes on the tops of their heads, the latter of which enable them to spot their prey from below—then quickly rise and strike. As if that didn’t make them terrifying enough, they can also deliver electric shocks and venom, according to the Florida Museum.

CONGO - CIRCA 1950s: A stamp printed in Congo showing Manylight Viperfish, circa 1950sEtiAmmos/Shutterstock

Viperfish (Chauliodus)

Images of these deep-sea dwellers (some species living at depths of 3,000 feet) are few and far between; this vintage engraved image adorns a postage stamp from Congo. The whole genus features hinged jaws that open at a 90-degree angle, with needle-like teeth; one 40-million-year-old species native to Australia actually has the largest teeth of any fish relative to its head size—they’re so big, in fact, that they don’t even fit in its head.

Giant Spider Crab on black backgroundLerner Vadim/Shutterstock

Japanese spider crab (Macrocheira kaempferi)

The largest anthropods on Earth, according to National Geographic, spider crabs live at depths of 1,000 feet (although some have been found as deep as 1,800 feet) in Pacific waters around Japan. Some grow as monstrously large as 12 feet from the tip of one claw to the tip of another. They live up to 100 years—just like these 10 other longest living animals—scuttling around the ocean floor to find their food—although they often lose a delicate limb or two in their lifetimes.

wolffish [family Anarhichadidae] behind dusty glass at sea life, fish looking at the cameraSimbert Brause/Shutterstock

Atlantic wolffish (Anarhichas lupus)

Five-foot-long bucktoothed natives of the North Atlantic, this species lives among the rocks at around 1,600 feet off the coast in places like Maine, where it forages for its dinner of crabs, sea urchins, and mollusks. No shell is too hard for the wolffish; its large head with strong jaws allow it to crush the exoskeleton of the most tenacious critter.

Six Gill Shark PupGreg Amptman/Shutterstock

Sixgill shark (Hexanchus griseus)

The sixgill shark (a juvenile of the species is shown here) swims around in the serious deep—up to 8,200 feet, according to National Geographic—biding its time till nightfall when it rises to the surface of the ocean to feed. Top favorite meals for this 16-foot predator: rays, squid, crab, and other sharks. It’s not just our oceans that are filled with unusual creatures, read on to find out the strangest animal living in each state.

Lela Nargi
Lela Nargi is a veteran journalist covering science, sustainability, climate, and agriculture for Readers Digest, Washington Post, Sierra, NPR, The Counter, JSTOR Daily, and many other outlets. She also writes about science for kids. You can follow her on Twitter @LelaNargi.