A professional windsurfer died in the sea off the Sussex coast last June because he did not realise how cold the water was, an inquest has heard.
Andy Funnell competed in windsurfing events around the world
The body of Andy Funnell, 21, was washed up on the shore near Bexhill, eight days after he vanished while riding a jet-ski wearing only shorts.
An inquest on Tuesday heard he suffered a rare form of shock to his heart due to the sudden exposure to cold water.
A verdict of misadventure was recorded by the coroner at Eastbourne.
Speaking after the hearing his father, Trevor Funnell, said he had been surfing in the Mediterranean just two days before his death.
"He did not consider that the temperature was going to be so different," he said.
"It is just a moment's misjudgement. He did not realise how cold the sea really was.
"There is no confusion about what happened," he said.
The inquest at Eastbourne Magistrates Court heard how the British Windsurfing Champion died on one of the hottest days of the year.
Giving evidence, Thomas Chambers said his friend came off the 600c machine off the coast of Seaford, where he lived, at about 1900 BST on 15 June when the sea was very calm.
Andy Funnell had perfected a "double jump" for competitions
Other friends swam out to find him, while a search by coastguard and lifeboat teams was launched.
East Sussex coroner Alan Craze said Mr Funnell's death should act as a reminder to others about how dangerous the sea can be.
"This case should be a reminder that the sea is an extremely hostile place and must be approached with the greatest caution," he said.
Mr Funnell was introduced to windsurfing by his father at the age of nine and had competed in windsurfing championships all over the world.