The deepest place in the ocean is called Challenger Deep, and it is in the Pacific Ocean, where NOAA gives its depth as about 10,935 meters (35,876 feet), as of November 2026. By comparison, the average ocean is about 3,682 meters (12,080 feet) deep, as of November 2026. The Mariana Trench is a long, deep trench in the floor of the western Pacific Ocean, near Guam, and it is an arc-shaped trench more than 2,540 kilometers (1,580 miles) long, with an average width of about 69 kilometers (43 miles). It formed by subduction, where the Pacific Plate is forced below the smaller Mariana Plate.

The hadal zone is the deepest part of the ocean, and it is found in deep trenches, below about 6,000 meters (19,700 feet). Below 1,000 meters is the midnight zone, which reaches down to about 4,000 meters, and below it is the abyss, which is cold and dark with crushing pressure, yet animals and microbes live there. Where one zone ends and another begins depends on who is measuring. Zone boundaries differ a little by source: the Smithsonian puts the abyssal zone at 4,000 to 6,000 meters, while Woods Hole gives 3,000 to 6,500 meters. In the abyss the pressure can reach about 600 times the pressure at sea level.

In 1960, Jacques Piccard and Don Walsh were the first people to go to the bottom of Challenger Deep, in a deep-diving craft called Trieste. In 2012, the filmmaker James Cameron dived alone in a one-person submarine, Deepsea Challenger, and his descent to Challenger Deep took 2 hours and 36 minutes. In April and May 2019 Victor Vescovo piloted the submersible Limiting Factor alone to the bottom of Challenger Deep, where pressure sensors averaged 10,925 meters (35,843 feet). Alvin is a research submarine that carries up to three people to the deep sea floor, and its depth rating of 6,500 meters lets researchers reach about 99 percent of the ocean floor, as of November 2026.

Animals live even in the deepest trenches. The deep ocean is very cold, about 4 degrees Celsius (39 degrees Fahrenheit) on average, and deep-ocean life is under extreme pressure, from about 40 to over 110 times the pressure of Earth's atmosphere. Snailfish live deeper than any other fish scientists have found, in the deepest trenches. The deepest fish ever seen alive was a small snailfish filmed at 8,336 meters (27,349 feet) in a trench near Japan in August 2022. The deepest fish ever captured, two P. belyaevi snailfish, came from 8,022 meters (26,319 feet) in the Japan Trench in August 2022. You may have heard that nothing could live in the deepest, darkest, highest-pressure part of the ocean. In fact, these fish prove otherwise.

Animals in the deep deal with food in several ways. Marine snow is a shower of bits of food that slowly falls from the upper ocean to the deep, and many deep-sea animals eat it. As marine snow sinks, flakes clump into bigger pieces that fall faster, but the trip to the bottom can still take weeks to years. Sediment traps on the ocean floor show that about 815 million tons of carbon reach the ocean floor each year, mostly as marine snow. A 2012 study found that Mariana Trench amphipods have powerful wood-busting enzymes, which let them eat sunken plant debris.

A whale can feed the deep sea. When a whale sinks to the sea floor at the end of its life, it becomes a whale fall: food and a home for many deep-sea animals. Whale bone is about 60 percent fat by weight, up to 200 times the nutrients usually found at the sea floor, and bone-eating Osedax worms bore in to get it. The Smithsonian says scientists have found about 25 species of bone-eating Osedax worms since they were first discovered in 2002, and think many more exist, as of November 2026. Some whale falls can support a blanket of 45,000 worms per square meter, the highest animal density in the entire ocean.

Other food comes from chemicals. A hydrothermal vent is a place on the sea floor where very hot water comes out of the ground. Vents form where seawater seeps into cracks near hot rock, heats up and picks up metals, then rises and meets cold ocean water. Scientists first found hydrothermal vent communities in 1977, and were surprised by how many kinds of living things were there. At vents and some other places on the deep sea floor, tiny microbes make food from chemicals instead of from sunlight, which is called chemosynthesis. Giant tube worms live at deep-sea vents and have no mouth or stomach, because bacteria living inside them make food from vent chemicals for the worm. Hydrogen sulfide is normally poisonous, but Riftia tubeworms have blood hemoglobin that binds tightly to both oxygen and hydrogen sulfide, carrying them safely to their bacteria.

The deep sea makes up over 95 percent of Earth's living space, and it remains largely unexplored. NOAA says explorers have seen less than 0.001 percent of the deep ocean seafloor, as of April 2026, and that we know less about the ocean floor than we do about the surface of the Moon and Mars. Seabed 2030 is a project aiming to produce a complete map of the ocean floor by the end of the decade. Scientists think most kinds of ocean life have not yet been discovered or named. What other animals are waiting at the bottom?

Words to know

• trench: deep ocean valley
• subduction: sinking plate
• hydrothermal: hot-water
• chemosynthesis: food from chemicals
• submersible: small submarine