Andrew "Bart" Simpson, the British Olympic champion sailor, has died after his catamaran capsized off the coast of California.
The 36-year-old was training for the America's Cup when his vessel flipped over in San Francisco Bay, trapping him underneath for ten minutes.
Mr Simpson, who won a gold medal in men's sailing in 2008 and a silver in London last year, was brought to shore but doctors were unable to save him.
"It is with immense sadness that Artemis Racing confirms the tragic death of crewmember Andrew 'Bart' Simpson today in San Francisco," said Paul Cayard, the chief executive of the Swedish Artemis Racing team Mr Simpson worked for.
"Simpson...was trapped underneath the boat and despite attempts to revive him, by doctors afloat and subsequently ashore, his life was lost.
“The entire Artemis Racing team is devastated by what happened. Our heartfelt condolences are with Andrew’s wife and family.”
Mr Simpson, who was affectionately known as "Bart" after the television show character, was married to Leah Simpson and had an infant son, Freddie.
He was one of 12 people pulled from the water when the 72-foot catamaran flipped over near San Francisco's Treasure Island shortly after 1pm.
A support boat took him aboard and carried him to the nearby St Francis Yacht Club, where paramedics performed CPR. He died shortly afterwards.
One other crew member suffered minor injuries.
It remains unclear why the racing vessel flipped over but wind conditions were said to be stronger than normal. The bright red boat could yesterday be seen still flipped over in the bay.
He was appointed an MBE in 2009 for his services to sport.
Mr Simpson and sailing partner Iain Percy, a childhood friend, took gold in Beijing in 2008 after narrowly besting the Swedish team in the Star event.
The pair came in silver in the same event during the 2012 London Olympics, competing from the Isle of Portland in Dorset.
Mr Simpson was born in Chertsey, Surrey, and attended Pangbourne College in Berkshire before studying economics at University College London.
Many of his fellow Olympians took to Twitter to pay tribute, including Kate MacGregor, who compteed in female sailing in the 2012 games.
The Artemis team was in training for the annual America's Cup, which is due to begin on July 4 and run through until September. The Artemis team was due to challenge the Oracle Team USA for the trophy.