The Mariana snailfish lives in the Mariana Trench, the deepest known ocean trench and home to the deepest-living described fish species.
The species, Pseudoliparis swirei, occupies hadal depths of roughly 6,198 to 8,076 metres in the western Pacific. It was formally described in 2017 after specimens were collected using deep-water traps baited with mackerel.
This pale, tadpole-shaped fish survives crushing pressure, near-freezing temperatures and perpetual darkness. It lacks the gas-filled swim bladder common in many fish, while its soft tissues, incomplete bone mineralization and specialized proteins help it tolerate extreme depth.
A common mix-up is confusing the Mariana snailfish with unidentified “ethereal snailfish” filmed deeper in nearby trenches. Those fish may hold deeper observation records, but the Mariana snailfish’s established habitat is the Mariana Trench.