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Life in the deep sea: 7,700m down

23 February 2012 Last updated at 15:25 GMT

Four teams are diving to the deepest part of the ocean, the Mariana Trench, which lies 11km (seven miles) down in the western Pacific.

But while adventurers are looking to roll back this final frontier, scientists are also interested in the deep.

Here, Dr Alan Jamieson, from Oceanlab at the University of Aberdeen, describes the fish that live 7,700m below sea level.