The Mariana Snailfish (Pseudoliparis swirei) dwells over five miles below sea level in a world of crushing pressure and impenetrable darkness.

Is it any wonder it took so long to fully describe this eerily translucent and tadpole-shaped fish? Researchers from the University of Washington managed to collect 36 samples of fish from the depths of the Mariana Trench, the deepest part of the world's oceans. Baited traps set to free-fall from the surface of the sea took up to four hours to settle on the ocean floor, where they were quickly mobbed (video) by a host of bizarre fish, crustaceans and invertebrates.

After studying the specimens retrieved from two separate expeditions to the Mariana Trench, situated near the island of Guam, researchers have dubbed the fish “Pseudoliparis swirei”. The first part of the name denotes its place in the genus Pseudoliparis while the second part honors Officer Herbert Swire, navigator on the British ship HMS Challenger who discovered the Mariana Trench in 1875.

The fish themselves average just over 11cm (about 4.3 inches) in length and they look like oversized bleached tadpoles. Their eyes are tiny – while sunlight can't penetrate to their ultra-subterranean environment, many of the seafloor creatures they prey on are photo-luminescent.

“This is the deepest fish that's been collected from the ocean floor, and we're very excited to have an official name,” stated Mackenzie Gerringer, one of the researchers on the University of Washington's exploration team. “Here they are free of predators, and the funnel shape of the trench means there’s much more food,” added Thomas Linley of Newcastle University, co-author of the study published in the journal Zootaxa. “There are lots of invertebrate prey and the snailfish are the top predator. They are active and look very well-fed.” (via FishBase)