What is the deepest-dwelling fish?

The deepest-dwelling fish is an unidentified Pseudoliparis snailfish. In 2023, researchers filmed a juvenile snailfish at 8,336 meters in Japan’s Izu–Ogasawara Trench, setting the deepest confirmed fish-sighting record.

The fish was identified only to the genus Pseudoliparis, so it cannot confidently be assigned to a named species. The Mariana snailfish, Pseudoliparis swirei, remains the deepest-living described fish species, but it has been recorded to about 8,076 meters.

Snailfish are particularly suited to hadal environments. Their gelatinous bodies and pressure-tolerant biology allow them to survive in ocean trenches where pressure exceeds 800 times that at the surface.

Because the record-setting fish has not been formally identified to species, “unidentified Pseudoliparis snailfish” is the most precise current answer.