To ask what lives at the bottom of the ocean, start with how deep it is. Let us go down and see. 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. Below 1,000 meters is the midnight zone. It reaches down to about 4,000 meters. It has no sunlight at all and stays near 4 degrees Celsius. Far down in the deep ocean it is dark, because sunlight does not reach there.

Below the midnight zone is the abyss. It is cold and dark with crushing pressure. Yet animals and microbes live there. The deeper you go in the ocean, the harder the water above pushes down on you. The hadal zone is the deepest part of the ocean. It is found in deep trenches, below about 6,000 meters (19,700 feet).

The deepest place in the ocean is called Challenger Deep. It is in the Pacific Ocean. It lies in the Mariana Trench. This is a long, deep trench in the floor of the western Pacific Ocean, near Guam. NOAA gives its depth as about 10,935 meters (35,876 feet) in November 2026.

In 1960, Jacques Piccard and Don Walsh were the first people to go to the bottom of Challenger Deep. They went in a deep-diving craft called Trieste. Alvin is a research submarine that carries up to three people to the deep sea floor. It was commissioned in 1964. Scientists also use robot submarines called ROVs to explore the deep ocean. They steer each one from a ship.

Many animals in the deep sea make their own light. Making light like this is called bioluminescence. Deep-sea animals use their light to find food, to find mates and to protect themselves.

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.

A giant squid has eyes as big as dinner plates. Giant squid can be up to about 13 meters (43 feet) long.

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. 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

• abyss: deep dark zone
• hadal: deepest zone
• trench: deep sea valley
• bioluminescence: living light
• hydrothermal: hot-water

The short version

The deep ocean is dark and cold, and it holds animals that make their own light. As of November 2026, the average ocean is about 3,682 meters deep. NOAA gives the deepest place, Challenger Deep, as about 10,935 meters. People have explored only a small part of it.

Quick facts

• As of November 2026, the average ocean is about 3,682 meters (12,080 feet) deep.
• Below 1,000 meters is the midnight zone, with no sunlight at all.
• Many deep-sea animals make their own light, called bioluminescence.
• A giant squid has eyes as big as dinner plates.
• NOAA gives Challenger Deep as about 10,935 meters (35,876 feet) in November 2026.