A British Olympic sailor has died after a Swedish catamaran capsized during a training session for the America's Cup in San Francisco Bay.
Andrew "Bart" Simpson - a double Olympic medallist - was one of an 11-man crew on board the Artemis Racing catamaran, the team website said.
It said Mr Simpson, 36, from Sherborne in Dorset, was trapped under the boat and efforts to revive him failed.
Artemis is a Swedish team due to take part in the America's Cup.
On its website, Artemis Racing said: "It is with immense sadness that Artemis Racing confirms the tragic death of crewmember Andrew "Bart" Simpson today in San Francisco."
At a news conference by the Bay, Artemis chief executive Paul Cayard said it was a "tragic day" for the crew.
"We have a lot to deal with in the next few days in terms of assuring everybody's wellbeing," Mr Cayard said, as he offered his thoughts and prayers to Mr Simpson's wife and family.
Mr Simpson won the Olympic Star class gold with Iain Percy - his Artemis team boss - in Beijing in 2008 and they took silver in London in 2012.
Artemis said that doctors "afloat" with the team tried unsuccessfully to revive the British sailor after he was freed from the wreckage.
John Derbyshire, performance director of the UK's Royal Yachting Association (RYA), described Andrew Simpson as an inspiration to others.
"We're devastated by the news from San Francisco today," he said.
"Andrew is someone I've worked closely with since the age of 16. He was a great talent and a key figure in our World Class Programme over many years culminating in his well-deserved Olympic success.
"He was a huge inspiration to others, both within the British Sailing Team and across the nation and our deepest sympathies go out to his family at this terrible time."
Stephen Park, RYA Olympic Manager, described Mr Simpson as "a fantastic sailor who got the best out of everyone he sailed with".
San Francisco Fire Department spokeswoman Mindy Talmadge said that, following the capsize, two sailors were brought to shore and taken to the St Francis Yacht Club where paramedics performed CPR on one of them.
The other person's injuries were not life-threatening, she said.
The rest of the crew from the capsized boat were transferred to a support boat operated by Oracle Racing, which is defending its America's Cup title from last year, officials said.
Mr Simpson served as the Swedish team's strategist.
Lt Jeannie Crump of the Coast Guard said it was not yet clear what caused the 72ft (22m) boat to capsize.
She said that a commercial salvage boat would tow the vessel to Clipper Cove, between Yerba Buena Island and Treasure Island.
The America's Cup race is due to run from July until September.
It is believed to be the second time a sailor has died during training for the race.
In 1999, Martin Wizner of the Spanish Challenge was fatally injured after being struck on the head by a broken piece of equipment.