08/26/2011 08:34 am ET | Updated Oct 26, 2011

San Diego Shark Sighting Clears Beach

A swath of San Diego’s Mission Beach was closed Thursday after a lifeguard saw what he estimated to be 18-inches of a shark fin piercing out of the water.

Lifeguard Todd Rice told the San Diego Union Tribune that he was paddling his rescue board when he saw the fin about 70 yards away. An 18-inch fin could be consistent with a 15-foot shark.

Great White Sharks are frequently sighted off the shore of southern California. Last year, two White Sharks were spotted and filmed by a stand-up paddler not terribly far from Mission Beach, a densely packed site in summer.

Thursday's sighting prompted a huge hunt as helicopters were dispatched to look for the massive fish, but no evidence of the predator was found.

Though shark attacks are quite rare, they are more probable around beaches like Mission Beach, where people use kayaks, surfboards and any other water sports equipment that can make them look like a seal from below.