Sam Kanizay, 16, of Australia stood in the ocean to cool his feet. When he emerged, he was surprised to see that his legs were bleeding profusely. He hurried home, where his father tried in vain to stop the bleeding. He took his son to the hospital emergency room and doctors rushed to help.
Later, the father went to the same part of the ocean Sam had been swimming in to find out what had attacked his son. From Washington Post:
Kanizay returned to the bay and waded back to the same spot where Sam had stood — albeit with two wet suits on to protect his skin.
Using a pool net and some raw meat, he collected thousands of what looked like mites, each of them about 2 millimeters long.
“You know, nurses and doctors from the hospital weren't going to jump in and try to get these critters, right?” Kanizay said. “I thought that someone had to solve the puzzle as to what had eaten Sam's legs.”
Genefor Walker-Smith, a marine biologist at Museum Victoria in Melbourne, identified the creatures Kanizay had collected as lysianassid amphipods, minuscule scavenging crustaceans that are attracted to the chemicals emitted by decaying meat, the museum said in a statement.
Sometimes referred to as “sea fleas,” the amphipods will not cause lasting damage, she said.