This footage from the America's Cup official website illustrates just how challenging it can be to sail the boats taking part in the America's Cup series. It's the oldest sporting event in the world, having taking place off the Isle of Wight for the first time in 1851.
The type of craft Andrew Simpson was sailing on is the new AC72 super catamaran. It is 72 feet long and powered by a huge wingsail. This design of yachts are contesting the America's Cup for the first time. They are faster and harder to sail than the monohulls used in previous contests.
The catamarans needly a highly skilled sailing team to keep the power under control. In the choppy waters of San Francisco bay the crew have to try to stop the catamaran's pitch-polling. This happens when the bow digs into a wave and the yachts tip over.
More top news
Friday morning's forecast for the east of the region
Friday morning's forecast for the west of the region
Thursday night's forecast for the west of the region