The Czech free-diver, David Vencl, has broken a new record in Lake Sils near St Moritz.
A hole had to be made in the ice to allow him into the water.
Vencl reached a record-breaking depth of 51.2 meters.
The water temperature was between 1 and 4 degrees and the attempt took just under two minutes, which was a bit longer than his team expected.
Vencl says he was a bit more nervous than usual due to the depth and the cold.
When he returned to the surface he coughed a bit of blood, but a later hospital check showed he was fine.
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