Which fish lives at the greatest known ocean depths?

The hadal snailfish is the fish group recorded living at the greatest known ocean depths.

Snailfish have been observed in hadal trenches below 8,000 metres, including the Mariana Trench. In 2017, researchers filmed a snailfish at about 8,178 metres, setting a record for the deepest observed fish at that time.

Their soft, gelatinous bodies and reduced or absent swim bladders help them withstand crushing pressure. They feed on small crustaceans and other animals living in trench sediments, where food arrives from the upper ocean only in limited amounts.

The name “hadal snailfish” refers to snailfishes adapted to the hadal zone, the deepest ocean region. Anglerfish and viperfish are also deep-sea species, but they generally live far above the extreme depths occupied by trench-dwelling snailfish.