He had been snorkelling with a woman near the harbour when he got into difficulties around 7.30pm. She called for help and was brought ashore.
Coastguards and lifeboat crews from Seahouses and Craster located the man fairly quickly and he was flown by a rescue helicopter from RAF Boulmer to Wansbeck General Hospital but he was later pronounced dead.
Seahouses RNLI mechanic John Hanvey said: "The inshore lifeboat crew were able to locate the man pretty quickly and as they arrived at the scene the woman who was with him had just managed to get to shore.
"The crew got the man into the lifeboat and started CPR and mouth to mouth resuscitation on him straight away, continuing as they took him to shore and carrying on until the RAF Boulmer helicopter arrived to transfer him to hospital.
"Everyone did everything they could to try to save the man and on behalf of everyone at Seahouses lifeboat station, I'd like to extend our sympathy to the man's family and friends."