It's sizzling hot in San Diego, but the ocean's largest predator is keeping people away from the city's most popular beach. A 2-mile stretch of Mission Beach was closed after a lifeguard on a rescue board spotted a great white shark a few dozen yards away, the Los Angeles Times reports. Hundreds of swimmers were ordered out of the water. This is the first time a shark sighting has closed the beach "for as long as anyone can remember," a rescue department spokesman says. The beach will remain closed until authorities searching the area with boats and helicopters decide it's safe to go back in the water. (More San Diego stories.)