Authorities are searching for a missing swimmer after a possible shark attack off the coast of Marin County. The U.S. Coast Guard, National Park Service and other agencies first responded to Wildcat Beach on Sunday morning. Crews in the air, on boats, and on ATVs are searching for the person along the Point Reyes National Seashore. A group of people on the beach first reported the possible shark attack after seeing something happen to the person in the water.