Yes, and no. Yes, they do come into San Francisco Bay on rare occasions, but most of the time they stay out of the bay. Great whites are not considered a danger in San Francisco Bay. But there are 11 other species of sharks living in the bay. At certain times of year (mainly in October), there are lots of great white sharks swimming up and down the coast past San Francisco. Their hunting ground stretches from Half Moon Bay, south of SF, up to Stinson Beach in Marin County, and out to the Farallon Islands, 30 miles straight west of SF. This area is sometimes called the Red Triangle (!) because of the frequency of great white shark attacks there. Since the waters are too cold and rough for most swimmers, it's the surfers and divers that are usually the targets. Scientists suspect it's the wetsuits worn year round that cause the sharks to occasionally mistake humans for their usual prey, the sea lions and harbor seals.