It happened just off Oddicombe Beach in Torquay on Sunday.
Police just after midday yesterday after two divers were picked up from the sea in Babbacombe Bay.
One of the men was unconscious and was taken to Torbay Hospital but later died.
Formal identification has not yet been carried out but the man is believed to be from Exeter.
His family has been told.
Police are trying to work out what happened.