The man was swimming in the sea off Ardara, Co Donegal, when he got into difficulties at about 2pm on Saturday.
Gardai said the man was airlifted to Letterkenny hospital where he was pronounced dead.
Irish Water Safety has made repeated appeals for awareness of the dangers of swimming in areas without lifeguards, especially in open water, and the difficulty of swimming in cold water following a series of deaths in rivers, lakes and at sea.
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? email@example.com