Extremely rare black jellyfish have begun to invade beaches ranging from Ocean Beach to La Jolla, and an increase in encounters has resulted in an increase in stings. Lt. Andy Lerum of the San Diego Lifeguards told ABC 10News that the creatures can break "into thousands of pieces" when hit by the waves. One unlucky swimmer reported being stung "seven times in one swim," and that Mission Beach had been infested with "hundreds" of black jellyfish.

According to lifeguards, jellyfish sighitings are common at this time of year, as warmer water temperatures draw them closer to shore. However, Lerum says it's been years since the black jellyfish was last seen. He added that the increase in jellyfish encounters and stings are the result of more people cooling off in the water during the summer.

[via ABC 10News]