The usual cause of death for someone jumping from The Golden Gate Bridge in San Francisco would be multiple blunt force trauma.
The falling body is travelling at about 75m.p.h. and is suddenly forced to stop descending. Unfortunately, the internal organs do not stop and are often torn loose. Jumpers typically have lacerated aorta's, livers, spleen etc.
Basically, the impact kills most people because water is not a soft landing when people enter from a great height. If a body enters the water at an angle and feet first, the person may initially survive the fall, but will die from internal bleeding within minutes as a result of the above mentioned injuries.
Sometimes the person survives the fall only to plunge deeply into the water which forces air out of their lungs and salt water in, which will asphyxiate the jumper.