The Golden Gate Bridge leads to the Northern California coast, which is known for its desolate nature and stark beauty. The beaches are remote and frequently shrouded in fog produced by the cold marine air blowing inland across the heated land during the summer.
Ocean Beach is frequently chilly, which is a good thing considering the dangerous surf and currents.
The same is true for the beaches further north at Point Reyes National Seashore and surrounding areas. You really have to pick your beach days carefully. The best oceanic beach for swimming is Stinson Beach, and this is where many of the beach enthusiasts from San Francisco head during the summer when the sun is shining. It is quite a drive through the curvy mountain roads in Marin County. You can see the beach long before you reach it.