Swimmers and surfers aren’t the only ones enjoying the water at Half Moon Bay. The San Mateo County Sheriff’s office says sharks were spotted yesterday afternoon off the coast. Four sharks could be seen from the Ritz Carlton hotel to Pillar Point Harbor, prompting a warning to beach goers. Marine biologists tell KPIX that more and more young adult great whites are swimming close to the Northern California coast where the waters are warmer and they are likely sunning themselves. Advisory signs telling beachgoers to swim at their own risk are posted on beaches near where the animals were sighted.