After an intense football match Saturday in Australia, 16-year-old Sam Kanizay dipped his legs into the chilly waters off Melbourne’s coast, hoping to soothe his sore muscles. Half an hour later he stepped out, bleeding profusely from countless tiny bites.

The gory and bizarre situation is now making international headlines. The images of his feet and ankles (here and here) really are quite disturbing (you’ve been warned). But the incident left medical professionals initially confused and media reports garbled. Some blamed the vicious attack on wee crustaceans called isopods, or “sea lice,” but experts are trying to clear up that error.

In a press statement Monday, local authorities reported that marine scientists had identified the flesh-eaters as lysianassid amphipods, a type of scavenging crustacean sometimes called “sea fleas.” They’re not known for swarming and attacking people. But scientists have long studied their affinity for flesh and ability to sniff it out in warm, cool, deep, and shallow waters around the world. Typically, they descend upon carcasses of marine animals and munch away the meat, tiny bite by tiny bite.

The task of identifying the critters was made easier by Sam’s father, Jarrod Kanizay. After bringing his son to the hospital with the severe leg wounds, he returned to the scene of the attack, dropping chunks of raw steak into the water as bait. The meat was quickly swarmed by a large pack of small, carnivorous critters, likely recreating what happened to Sam. Jarrod scooped them up for experts to identify.

Museums Victoria marine biologist Genefor Walker-Smith determined they were sea fleas after examining them under a microscope. “It was just unlucky,” she said in a statement. “It’s possible he disturbed a feeding group, but they are generally not out there waiting to attack like piranhas.”

Scientists have described lysianassid amphipods as some of the most abundant and widespread scavengers in the seas—not to mention, they're also ferocious. There are more than 500 species and 112 genera. Some have wide-set, piercing incisors for ripping apart all kinds of bloody chow.

Walker-Smith speculated that the ones that attacked Sam may also possess an anti-coagulant, similar to peptides used by leeches. That may explain Sam’s excessive bleeding after the attack. An anti-coagulant combined with the low water temperatures may also explain why Sam didn’t feel the feeding frenzy at his feet.

Sam remained in the hospital Monday recovering from the wounding. On a positive note, Walker-Smith added that lysianassid amphipods are not known to be venomous and should cause no lasting damage.

It’s still unclear what caused them to swarm around Sam’s legs, though. Earlier research has suggested that lysianassid amphipods may have two strategies for flesh foraging: passively “hovering” until they sense an attractive chemical plume from flesh, or lying low in sediment until a body falls in their midst. Walker-Smith speculated to local media The Age that Sam may have inadvertently gotten too close to a fish carcass on which the fleas were feasting.

A spokesperson for the Department of Environment, Land, Water, and Planning of Victoria told The Age that sea fleas are a "common and natural part of a healthy marine ecosystem" that "keep our marine waters clean by consuming dead and dying marine animals... DELWP advises swimmers to wear a wetsuit with boots to reduce the risk of being exposed to sea fleas and avoid swimming at night," when the creatures are more active.