British Olympic gold medallist Andrew Simpson has been killed after Swedish America's Cup challenger Artemis Racing capsized their massive catamaran while training on San Francisco Bay today.
Veteran New Zealand America's Cup campaigner Craig Monk was also injured in today's capsize.
Simpson, one of the 11-man crew, was trapped under water when the catamaran capsized, according to a statement from the team.
Support boats, including a Team New Zealand boat that was in the area, rushed to the scene but were unable to revive Simpson despite attempts by doctors afloat and subsequently ashore.
It’s understood Monk was the other sailor hurt in the accident but his injuries were minor.
"The entire Artemis Racing team is devastated by what happened," CEO Paul Cayard said.
"Our heartfelt condolences are with Andrew's wife and family."
Simpson, 36, won a gold medal at the Beijing Olympics in 2008 and silver in London last year in the Star class.
He started his sailing career in the Laser before shifting to the Finn and winning a bronze medal at the 2003 world championships.
He then moved into the Star, winning world championship gold in 2010 and silver in 2012 to go with his bronze from 2007 before adding his Olympic triumphs.
He was appointed Member of the Order of the British Empire (MBE) in the 2009 New Year honours.
He is survived by his wife Leah and young son Freddie.
Artemis have New Zealander Monk as a grinder on their crew and three other Kiwis, Sean Clarkson (wing trimmer), Andrew McLean (grinder), Phil Jameson (pit) in their first-choice team.
Other New Zealanders listed in the Artemis squad are Rodney Ardern (wing trimmer), Stu Bettany (boat captain) and Troy Tindall (Foiling AC45, boat captain).
Monk is well known to New Zealanders, having won 18 national titles in five classes and medals at the Olympic Games and world championships. He was the Finn bronze medallist at Barcelona in 1992.
Aerial footage of the capsize showed the crashed boat with one of its two red hulls buckled and the massive wingsail, still connected, but floating alongside.
Although Team New Zealand AC72s are not yet operational in San Francisco, it's understood their chase boats, and also chase boats from the Oracle syndicate, rushed to the scene.
It's the second major accident in the leadup to this year's America's Cup following cup-holder Oracle destroying their first AC72 in a "pitch-pole" capsize last October.
Artemis have already had problems, damaging a wingsail when they were launching their first boat.
They have also had major design problems that forced the catamaran back into the builder's yard, in the hope of getting it up to pace with foiling, which looks to be a speed-key for all of their rivals.
Artemis are one of just three challengers for the Cup alongside Team New Zealand and Italy's Luna Rossa.
The Louis Vuitton Cup challenger series starts in San Francisco on July 4 with the winner to race Oracle for the America's Cup on September 7.
Team New Zealand crew are set to leave Auckland for San Francisco next week after a year trialling their two giant catamarans in Auckland with a testing programme notable for it being incident-free on the water.
Their only problem was when a gust of wind hit their wing-sail while it was being loaded on to the boat at their base in Auckland's Viaduct Basin.
But there have been concerns expressed about the wisdom of sailing the huge cats, which can hit speeds of around 45 knots, on the tight courses.
Stephen Barclay, CEO of the America's Cup Event Authority, said officials were investigating Thursday's accident.
He said it was unclear what effect the death will have on the America's Cup races, which are scheduled to run from July to September.
It was too soon to answer questions about the safety of the high-tech boats on the San Francisco Bay, Barclay said.
''Obviously a catamaran is more prone to capsizing than a mono-hull,'' he said. ''Whether boats are safe or unsafe, we're not going to speculate on those things.''
In addition to sailors wearing crash helmets and life vests, chase boats carry doctors and divers, Barclay said.
''There are lots of precautions that are taken, and some of those are as a result of Oracle's mishap last year,'' he said.
San Francisco Bay also provides some unique challenges, especially when wind and tide collide, making for rough surface conditions.
Other America's Cup combatants have expressed their sympathy to Artemis and Simpson's family.
Team New Zealand managing director Grant Dalton said the team extends its condolences to Andrew Simpson’s family, friends and to the Swedish team.
Oracle, the current holders of the America's Cup released the following statement:
“Today is a sad day for all of us in the sailing community. Andrew Simpson was a great person, a terrific sailor, and a good friend to all of our team. Our thoughts are with his family and the entire Artemis team. He will be dearly missed.”
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.
- Fairfax NZ with AP