The latest trend hitting California beaches? Sharks. On Saturday alone, there were not one, but two shark sightings off the coast: one in Morro Bay, near San Luis Obispo, and another one farther down the coast in La Jolla. And, according to scientists, there's reason to worry about the scary pattern. The Morro Bay incident left surfer Elinor Dempsey (above) with a gnarly souvenir: a shark bite on the side of her board. Luckily, Dempsey was unharmed by the attack. "First I thought it was a dolphin, and I thought, What the hell is he doing?” she told The San Luis Obispo Tribune. “And he kind of landed on my board. Then I realized he had taken a chunk." The La Jolla sighting was less dramatic, but resulted in the chilling video below captured by kayakers. The footage shows a hammerhead shark swimming aggressively around — and bumping into — their kayaks. Here comes the bad news: These episodes may not be one-off events. An unusually strong El Niño — a weather phenomenon that occurs when the Pacific Ocean gets warmer than usual — is to blame, according to some scientists. The El Niño has changed sharks' migration patterns. Instead of migrating south to Mexico, the sharks are sticking around Southern California's warm waters. So, we might be seeing more and more of the frightening creatures, as the El Niño is only getting stronger. So on that lovely note, Labor Day beachgoers: You might want to be extra cautious this weekend.