A ghostly white fish likely had no idea it was breaking a record when it swam past a camera more than eight kilometres below the surface of the ocean.

The Mariana snailfish was filmed at a depth of 8,178 metres in the Mariana Trench, the deepest part of the world's oceans in the western Pacific Ocean.

That makes it the deepest fish ever recorded, said the Japan Agency for Marine-Earth Science and Technology in a news release this week.

Video footage of the fish was captured in May using a high-resolution video camera attached to a "lander" robot designed specifically for the crushing pressures of the "hadal" zone below a depth of 6,000 metres. The lander had been launched by JAMSTEC's research vessel Kairei.

The fish, along with other organisms — such as shrimp-like creatures called amphipods — were lured in front of the camera using mackerel as bait.

The Mariana snailfish is not a new species — it had been described by U.S. and U.K. scientists in 2014 after being spotted as deep as 8,076 metres.

But now that it's been recorded more than 100 metres deeper than before, it breaks a record announced by the Chinese Academy of Sciences, which reported that it had recorded a lion fish at a depth of 8,152 metres earlier this year.