Officials said winds were blowing between 15 and 20 knots (17 to 23 mph) when the boat capsized. The National Weather Service later 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 near Treasure Island, which is bisected by the Oakland-San Francisco Bay Bridge. The armada of rescue boats and helicopters were visible from the roadway.
Simpson and the unidentified injured sailor were brought to shore at 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 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. The team announced Feb. 23 that Simpson was joining Artemis to "provide weather and tactics support" to the crew.
Artemis Racing 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.
The team 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.