Snailfish are known to thrive at extreme depths: another variety, Pseudoliparis amblystomopsis, previously held the undisputed record for deepest-living fish at 7703 meters. Handling the intense pressure of the deep sea is a challenge for most animals because it impedes muscles and nerves and bends proteins out of shape, disrupting the working of enzymes required for life.

But this creature, which was filmed several times at a depth of 8,143 meters, or 26,715 feet, has a different body shape from known species of snailfish, so it might be something else entirely. But one thing is for certain, the scientists told the BBC — it's definitely not a species we've seen before.

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"We think it is a snailfish, but it's so weird-looking; it's up in the air in terms of what it is," Alan Jamieson of the University of Aberdeen told the BBC. "It is unbelievably fragile, and when it swims, it looks like it has wet tissue paper floating behind it. And it has a weird snout — it looks like a cartoon dog snout."

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So how do these ghostly fish manage to live at these crushing depths? Deep-sea fish have higher levels of a chemical called trimethylamine oxide (TMAO). TMAO helps proteins maintain their shape as pressure mounts. Fish shouldn't be able hold enough TMAO in their cells to live below around 8,200 meters, according to recent research by Jamieson — so these new fish may very well be some of the very deepest.

Update:

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While these new fish are indeed the deepest ever seen on film, there's a single fish that stands in the way of their deep-sea domination: In the 1970s, a solitary cusk eel was trawled up from a depth of 8,370 meters. Since it wasn't observed on camera down in the water, we don't know whether it was one of many living comfortably at that depth -- as was the case for these new fish at 8,143 meters. And since none have ever been found at that depth again, it's possible that the record-breaking eel was actually caught higher up.

But whatever the secrets of the cusk eel, the deepest depths of the ocean are an inhospitable place to soft-bodied creatures. And these strange new fish seem to like the water fine.