America's Cup 2013 two finalist hydrofoil catamarans "Oracle Team USA" and "Emirates Team New Zealand" racing neck and neck on the San Francisco Bay.
The sail of the AC72-class hydrofoil catamarans is a rigid wing made of carbon fiber. When hydro-foiling, those sailboats can go about twice as fast as the wind.
For more photos and info about the America's Cup race and the AC72-class hydrofoil catamarans, go to the album description.