Sea Bug Bites

When you go swimming at the beach, your biggest concern is probably whether you’ll get a sunburn—not that you’ll leave the water covered in blood! But that’s exactly what happened to 16-year-old Sam Kanizay. He went for a dip off the coast of Melbourne, Australia, last August and emerged with bloody legs.

After Sam’s dad, Jarrod Kanizay, washed off the blood, he saw hundreds of tiny holes in his son’s skin. “By the time we got to the hospital, Sam’s legs were covered in blood again,” says Kanizay. The wounds wouldn’t stop bleeding.

Kanizay wanted to learn what caused his son’s injuries. So he took a piece of raw meat to the same spot where Sam had waded into the water. A horde of creatures swarmed the meat. Kanizay collected some of the animals and took the sample to Genefor Walker-Smith, a marine biologist at Museums Victoria in Melbourne. She identified the flesh-munching culprits as sea fleas.

Sea flea is a common name for an amphipod. Many of these tiny, shrimp-like creatures are scavengers that feed on dead animals in the ocean. But on rare occasions, they go after live prey. And when the animals find something meaty, they can quickly swarm—as they did in Sam’s case.

Because Sam was standing in cold water that numbed his legs, he didn’t feel the creatures attacking. But Walker-Smith says most people quickly know when sea fleas bite and brush them off. Fear of a sea flea attack shouldn’t keep you out of the water, she adds.