Artemis Racing said Andrew "Bart" Simpson died after the capsized boat's platform trapped him underwater for about 10 minutes shortly after 1 p.m. Artemis and two other yacht teams each outfitted with multimillion-dollar racing boats that can achieve speeds of 45 mph are challenging defending champions Oracle Racing for the America's Cup, sailing's most prestigious trophy.
Simpson, 36, served as the Swedish team's strategist.
Artemis said doctors "afloat" with the team and on shore were unable to revive Simpson after he was freed from the wreckage. The other sailor suffered minor injuries, and the rest of the crew of about a dozen was accounted for and taken back to their dock in Alameda.
"The entire Artemis team is devastated by what happened," CEO Paul Cayard said in a statement posted on the team's website. "Our heartfelt condolences are with Andrew's wife and family."
Officials said winds were blowing between 15 and 20 knots when the boat capsized. The National Weather Service later in the day issued a small-craft advisory, warning inexperienced mariners to stay off the bay and indicating winds of between 21 knots and 33 knots.
The Artemis boat flipped in winds of about 20 knots near Treasure Island, which is bisected by the Oakland-San Francisco Bay Bridge. The armada of rescue boats and helicopters were visible from the bridge.
Simpson and the unidentified injured sailor were brought to shore as the St. Francis Yacht Club in San Francisco, where paramedics performed CPR on Simpson. He was pronounced dead a short time later.
This is the second time a sailor has died during training for the America's Cup. In 1999, Martin Wizner of the Spanish Challenge died almost instantly when he was hit in the head by a broken piece of equipment.
No deaths have been recorded during the actual racing since its inception in 1851.
Simpson and his partner Iain Percy won an Olympic gold medal for England in 2008 in the so-called Star class of sailing. The duo was expected to repeat in London in 2012 but was upset by a Swedish team and settled for silver.
Percy is Artemis' director and the boat's tactician. Artemis announced on Feb. 23 that Simpson was joining the team to "provide weather and tactics support" to the crew.
A month later, Simpson tweeted: "Moving the family to San Fran for 6 months is pretty hectic!!! The cup should be fun though!!"
Artemis has had its share of upheaval in the buildup to the 34th America's Cup. Late last year, skipper Terry Huthinson of Annapolis, Md., was released. He was replaced by Nathan Outteridge of Australia, who won a gold medal at the London Olympics.
Artemis has had technical problems, as well. Last fall, Artemis said the front beam of its AC72 catamaran was damaged during structural tests, delaying the boat's christening. A year ago, Artemis' AC72 wing sail sustained serious damage while it was being tested on a modified trimaran in Valencia, Spain.
This also wasn't the first America's Cup boat to capsize on the hard-blowing San Francisco Bay. Oracle's $10 million boat capsized in 25 knot winds in October, and strong tides swept it 4 miles past the Golden Gate Bridge. No one was injured, but the rough waters destroyed the 131-foot wing sail and the boat was sidelined until a new sail shipped from New Zealand was installed in February.
The boats participating in the latest America's Cup more resemble a space craft than the traditional sloop-shaped yachts that historically competed for the trophy.
Financed by billionaire Larry Ellison, Oracle Team USA won the 2010 cup and made several changes to the races this year in an attempt to make the staid competition more fan- and TV-friendly.
While much faster and more exciting than the sloops, the catamarans have proved hard to handle. The wing sail looks and acts like an airplane wing, improving the yacht's speed and maneuverability. The seven-ton boat's hulls are lifted out of the water and it skims along the waves on "foils," reducing the drag on the boat and increasing speed dramatically.
Because the boats are cutting-edge, sailors wear crash helmets and life vests.
Coast Guard Lt. Jeannie Crump said the agency did not know the extent of the damage to the boat. She said a commercial salvage boat was at the scene and would tow the vessel to Clipper Cove, between Yerba Buena Island and Treasure Island.
Crump added Coast Guard officials weren't sure what caused the boat to capsize. She said the Swedish team has two boats.
The America's Cup race is scheduled to run from July through September, and the teams are training in the bay.
Associated Press writers Paul Elias and Garance Burke in San Francisco, and Bernie Wilson in San Diego contributed to this report.