The Challenger Deep is the deepest known point of the seabed in the Earth's hydrosphere, with a depth of 10,902 to 10,929 m by direct measurement from deep-diving submersibles, remotely operated underwater vehicles, and benthic landers and slightly more by sonar bathymetry.

What is under the Challenger Deep?

That's 1.7 miles down! The average depth of the ocean is about 12,100 feet . The deepest part of the ocean is called the Challenger Deep and is located beneath the western Pacific Ocean in the southern end of the Mariana Trench, which runs several hundred kilometers southwest of the U.S. territorial island of Guam.

What did they see at the bottom of the Challenger Deep?

They saw arrowtooth eels at 9,843 feet (3,000 m) and a wriggly little spoon worm (Echuria) at 22,966 feet (7,000 m). At 26,247 feet (8,000 m), they observed Mariana snailfish and supergiant amphipods (Alicella species) — creatures about 20 times larger than typical amphipods.