MARIN COUNTYA second sighting of a great white shark off Stinson Beach has prompted the National Park Service to prohibit water use through the Labor Day weekend."We had another sighting about 6:30 p.m. Thursday night by two visitors," said Chris Powell, park service spokeswoman. "Our lifeguard interviewed them and felt it was a credible sighting."The news puts a damper on what normally is a busy holiday weekend at the beach. Typically thousands of people from around the Bay Area … [Read more...]