Visitors returned to Mission Beach on Saturday after possible shark sightings prompted two days of closures, lifeguards said.Lifeguard Nick Lerma said it was "business as usual" as surfers, swimmers and boogie boarders returned to the area around tower 13, where a surfer spotted a 14-inch dorsal fin, which was feared to belong to a shark. He said people were back in the water, although many stayed in shallower areas near the shore.Lerma also said lifeguards are monitoring the situation closely."We're remaining vigilant," he said. "That's what we do. We have all the towers opened up main observation tower, rescue boat and personal watercraft."The owner of a Mission Beach rental business said people did not seem to let the scare affect their beach plans and beachgoers were upset when they were not allowed in the water."They didn't quite believe it," the man said, preferring not to give his name. He said his customers were unsure "if there really was a shark out there," and that being forced out of the water was more of an inconvenience. Despite shark sightings in consecutive days, beachgoers seemed unconcerned."I was more concerned of driving on the L.A. freeway then I was of getting attacked by a shark," one beachgoer told 10News.Eight-year-old Calvin Tomsie had a different reason for not worrying."Sharks don't like to eat people," he said. "You taste like pizza to them and they don't like pizza."Though no research supports Tomsie's theory, Lerma said research does indicate more sharks could be in the area because of the warm water."Larger females will be in the area," said Lerma. "They'll pup, there'll be a birth, and then they'll move north."The area was closed Thursday afternoon after lifeguard spotted an 18-inch dorsal fin, but was later reopened to beachgoers, Lerma said. A fin that size could belong to a shark at least 10 feet long, he said.Lifeguards closed the two-mile stretch of water again Friday when an experienced surfer spotted a 14-inch dorsal fin in the water, San Diego lifeguards said.The fin was spotted about 8 a.m. Friday about 100 yards from tower 13, according to the San Diego Fire-Rescue Department. The waters were closed in one mile in each direction from the location of the sighting.Lerma said two credible people reporting different sightings in the same area was very rare."We've had a few reports over the last decade but nothing like this nothing as credible," he told 10News.No further sightings were reported and the area opened to beachgoers at 8 a.m. Saturday, Lerma said.Hot weather may contribute to the crowds at the beach, where the water was 64 degrees, Lerma said. The National Weather Service forecast temperatures upwards of 114 degrees in parts of the county.