What lives at the bottom of the ocean? First, how deep is it? As of November 2026, the average ocean is about 3,682 meters (12,080 feet) deep. People have explored only a small part of the deep ocean. Scientists think most kinds of ocean life have not yet been discovered or named.

The twilight zone is the ocean layer from about 200 to 1,000 meters (656 to 3,280 feet) down. Only a little light reaches it. Far down in the deep ocean it is dark, because sunlight does not reach there. The deep ocean is also very cold. It is about 4 degrees Celsius (39 degrees Fahrenheit) on average.

The Mariana Trench is a long, deep trench in the floor of the western Pacific Ocean, near Guam. The deepest place in the ocean is called Challenger Deep. It is in the Pacific Ocean. Now let us meet some of the animals that live in the deep.

You may have heard that nothing makes light down there. In fact, many animals in the deep sea make their own light. Making light like this is called bioluminescence. A deep-sea anglerfish has a glowing lure. It dangles in front of its mouth. The glowing tip of the lure holds bacteria that make light.

Next, let us meet a squid from the deep. Here is a big one. A giant squid has eyes as big as dinner plates. Giant squid can be up to about 13 meters (43 feet) long.

Now let us go to the sea floor. A hydrothermal vent is a place on the sea floor. Very hot water comes out of the ground there. Giant tube worms live at deep-sea vents. They can grow almost five feet long.

Marine snow is a shower of bits of food. It slowly falls from the upper ocean to the deep. Many deep-sea animals eat it. A vampire squid has two long, sticky threads. It catches bits of falling marine snow with them. Then it pulls the bits through its arms to eat.

Here is another kind of food in the deep sea. When a whale sinks to the sea floor at the end of its life, it becomes a whale fall. A whale fall is food and a home for many deep-sea animals.

Words to know

• twilight: dim zone
• trench: deep sea valley
• bacteria: tiny living things
• lure: dangling bait
• hydrothermal: hot-water