Calum Mackay, 45, was swimming off the coastal resort Koh Samui when he was dragged out to sea by the stream of water flowing out from the beach.
The kitchen-firm boss, from Aberdeen, had travelled to a secluded island with his wife Helena to celebrate her recent graduation from university.
Mrs Mackay said there were no warnings of rip currents on the beach where her husband had been swimming.
A rip is a strong current at the point where water from waves arriving on the beach flows back out to sea. The surface of the rip often looks calm but they are capable of sweeping the strongest swimmers out to sea .
Mr Mackay's cousin, Craig Mackay, said: "Calum was one of life's gentlemen and we will all miss him greatly. Helena is desperately upset.
"It's so sad what was supposed to be a happy occasion turned out to so tragically. It's hard to come to terms with."
He added: "We don't know exactly what happened, the currents in that part of the world can be lethal, as we so dreadfully found out."
The Foreign Office said Mr Mackay's family has had consular assistance since the tragedy on November 30.