What lives under the sea?

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Humans have explored and discovered almost all of the land, but the land under our feet is only a small part of the world. The oceans make up more than 95% of Earth's living space, yet 80% of this vast realm remains unexplored and untouched.

How do we know what's under the sea? The truth is, we don't. Scientists believe there are as many as 10 million marine species undiscovered. But the ones unearthed recently in the world's deepest, darkest trench have proven to be pretty remarkable.

Explore the deepest part of the planet, including the creatures that live under the sea and the creepiest creatures of the deep.

What is a marine zone?

what lives at the bottom of the ocean 1
The ocean is divided into several regions: Sunshine, Twilight, Midnight, Deep Ocean, and Ultra Abyss. The abyssal zone is the deepest place in the ocean.

©PHOTO JUNCTION/Shutterstock.com website

To better understand and study this underwater dominance, scientists have divided the oceans into several regions: Sunlight, Twilight, Midnight, Deep Ocean, and Ultra-Abyssal. The sun is the area closest to the surface, while the abyss is the deepest part of the ocean. Different creatures live in different areas, and most of the ocean is untouched by humans.

sun belt

The pelagic or solar belt extends down more than 600 feet from the surface. This area is known as the sun zone because enough sunlight penetrates the water's surface for photosynthesis. The Sunshine Zone is home to a variety of marine species such as sharks, jellyfish and turtles. This sea area is rich in plant and animal life.

fuzzy zone

If your trip exceeds 650 feet, you will enter the mesopelagic zone, commonly known as the twilight zone. This ocean space has little light, increasing to 3,280 feet (more than half a mile below the surface). Photosynthesis does not take place in this area, so animals feed on fallen food particles or prey on victims in sunny areas. Animals in the twilight zone include lanternfish, viperfish, and mesopelagic jellyfish.

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Facing a variety of predators—including fish, birds, and whales—the blanket octopus is a master of camouflage.
Creatures such as octopuses and eels live in the midnight zone, 13,000 feet below the surface.

©Sam Robertshaw/Shutterstock.com

midnight zone

The pelagic or midnight zone ranges from 3,200 feet to over 13,000 feet. The sun doesn't reach this area, and the average temperature is 39 degrees Fahrenheit. The cold, dark waters are home to creatures such as monkfish, vampire fish, octopus and eels.


The pelagic zone, or abyssal zone, begins at 13,000 feet, extends over 19,000 feet (3.7 miles below the surface), and ends at the ocean floor. This area covers 83% of the ocean and 60% of the Earth's surface. With little oxygen, no light, frigid temperatures, and extreme pressure, it's a miracle that life can still exist in this part of the world. Organisms that inhabit the deep ocean include chemosynthetic bacteria, worms, small fish and some species of sharks.

deep sea creature viper fish
Small fish, worms and certain shark species live in the deep ocean up to three miles below the surface.

© superjoseph/Shutterstock.com

Abyss area

The Hedalpelagic, or superabysmic zone, is the deepest part of the ocean and consists of trenches on the ocean floor. The word hadal translates to Hades, the ancient Greek god of the underworld. The area is not continuous, but contains 13 troughs and 33 trenches (all seafloor depressions). The trench has an average depth of 9,000 to 13,000 feet. However, there are at least five trenches deeper than 32,000 feet (over 6 miles)!

How deep is the ocean?

The average depth of the ocean is 12,100 feet (over two miles). However, the last time measurements were made in 2010, oceanographers had only mapped 10 percent of the ocean floor. So, the depth is only an estimate.

That measurement is for average depths, though, and doesn't reflect the deepest parts of the ocean, which are much lower.

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What is the Mariana Trench?

The Mariana Trench is the deepest point in the ocean.

© iStock.com/ratpack223

The Mariana Trench is the deepest ocean trench in the world, more than seven miles below the surface of the Pacific Ocean. At the southern end of the Mariana Trench is Challenger Deep, the deepest ocean known to man. The deepest part of the trench is 35,876 feet, and the Mariana Trench itself is 1,580 miles long, more than five times the length of the Grand Canyon.

What lives under the sea?

Japanese spider crab deep sea creature
Sea spiders, giant squid and tube worms live on the bottom of the ocean.

© LELACHANOK/Shutterstock.com

Sea spiders, giant squids, tube worms and cookie sharks are some of the creatures that live under the sea. Animals living at these depths had to evolve to withstand enormous pressures (600 times higher than at sea level). There are even sea creatures that scientists have yet to identify.

There are no plants on the seabed. Plants need oxygen and sunlight to grow, and the deep ocean has neither. Scientists have discovered a snailfish at 27,000 feet below sea level, the deepest living fish ever found.

Here is a list of creatures that live under the sea:

  • tripod fish
  • Sagefish
  • sea cucumber
  • octopus
  • snail fish
  • zombie worm
  • Arowana
  • goblin shark
  • pelican eel
  • anglerfish
  • ax fish
  • frilled shark
  • squid
  • sponge
  • comb jelly
  • Pink Perspective Fantasia
  • Spikefish

What is the scariest creature in the deep sea?

spotted cuckoo

Blobfish can grow to over two feet long and are more ghoul-like than fish-like.

© Lack of Author Information/Public Domain – License

This slimy, ghoul-like creature lives in the deep sea along the Pacific coast. These blob fish may be unsightly, but they are harmless to humans. They feed on crustaceans and molluscs and can grow to over two feet in length.

goblin shark

The stupidest animal in the world: goblin shark
Goblin sharks are descended from a family of sharks that lived 125 million years ago.

© Peter Halasz / CC BY-SA 3.0 – License

When you think of the dark ocean under the sea, you think of scary sea creatures. Goblin sharks fit exactly that description. It's more reminiscent of a dinosaur than anything you'd expect to find in modern times. It has long serrated tusks protruding from its mouth, small round eyes and a long nose impressively. Goblin sharks are direct descendants of prehistoric sharks (125 million years ago) and can grow up to 20 feet.

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Nemertea are the phylum of invertebrates also known as tape worms or proboscis worms that can grow up to 100 feet!

©Rattiya Thongdumhyu/Shutterstock.com

Is it an alien or a sea creature? These translucent worms are usually only a few feet long, but some can grow up to 100 feet! They also shoot a web-like structure called a proboscis from their mouths. It helps them stalk prey or deter predators. The proboscis forages on the seafloor and has few natural enemies.

giant isopod

deep sea creature giant isopod
Giant isopods resemble pill bugs that eat whale carcasses.

©kikujungboy CC/Shutterstock.com

Giant cockroaches are the stuff of nightmares and horror movies, but what if they really existed? While not technically a cockroach, giant isopods are more like pill bugs or wood bugs. Still, this isopod was gigantic. They crawl along the icy bottom, hoping to devour whale carcasses and dead squid floating on the ocean floor.

frilled shark

frilled shark
Frilled sharks will swallow their prey whole, and will even eat other sharks!


The frilled shark has 300 rows of needle-like teeth and an eel-like body. It has prehistoric ancestry and is known for hunting prey near the surface, swallowing it whole with its long, flexible jaws. The frilled shark's favorite food is squid, but it will eat other sharks as well.


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More from AZ Animals

featured image

Animals with big eyes - giant squid
The giant squid has huge eyes that help it find prey in the dark depths of the ocean.

© Rui Palma / Shutterstock.com

about the author

Niccoy is a professional writer and content creator focusing on nature, wildlife, food and travel. She graduated from Florida State University with a business degree before realizing that writing was her true passion. She lives in the foothills of the Rocky Mountains and loves hiking, reading and cooking!

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