The attack took all of half an hour.
That's about how long Sam Kanizay says he spent relaxing waist-deep in the waters of Melbourne, Australia's Brighton Beach on Saturday. The 16-year-old had been footsore from a round of soccer, he says, and the cold water felt pleasant as he absently listened to songs on his iPhone.
It was only when he finally waded out of the water that he discovered what had happened to him: Blood streamed from thousands of tiny pinpricks that littered his legs from the ankle down. And as he hobbled back to his house nearby, he and his father discovered something just as unsettling.
"There was no stopping the bleeding," his father, Jarrod Kanizay, told The Washington Post. "We just had to get him to hospital."
Eventually, medical professionals were able to stabilize the situation and slow Sam's bleeding. What took longer, however, was simply figuring out what in the world had caused that bleeding. Doctors and scientists alike were stumped. By the next day, the mystery had made international news.
So, with his son still hospitalized, Jarrod waded out to the same spot the next night — clad in a wetsuit for protection — holding some raw meat in a net. Then, he waited.
"You know, nurses and doctors from the hospital weren't going to jump in and try to get these critters, right?" he told the Post. "I thought that someone had to solve the puzzle as to what had eaten Sam's legs."
When he emerged from the water, he found a bunch of tiny creatures had swarmed the meat — creatures he kept and carried back to land for tests.
One thing was immediately clear to Jarrod Kanizay, as he told The Associated Press: "These little things really love meat."
Unsettling videos of the little guys devouring chunks of meat demonstrated at least that much. But for a while, that's about the only thing that was clear.
"I've never seen anything like this," one marine expert told a local TV program. Thomas Cribb, a parasite expert from the University of Queensland, told the AP that the creatures were "not a parasite I've ever come across."
Still, the Museums Victoria, a consortium of state-owned museums in Melbourne, declared Sunday they believe they had cracked the mystery. After testing the creatures captured by the father, marine biologist Genefor Walker-Smith identified them as lysianassid amphipods, "a type of scavenging crustacean."
The little crustaceans, often known as "sea fleas," are "naturally-occurring scavengers, which commonly bite but do not usually cause these kind of injuries," the organization posted on Facebook.
"It's possible the amphipods contained an anti-coagulant, which would account for the inability to stop the flowing blood and that the very cold water may be the reason Sam didn't feel the bites. The amphipods have no venomous properties and will not cause lasting damage."
The news surely comes as a relief to the Kanizays. But for now, rest remains the order of the day. Sam was still hospitalized as he recovered from the ordeal.
Should others be concerned, though? Walker-Smith suspects not, as she says the behavior is a little out of character for the sea fleas.
"It was just unlucky," she told The Australian. "It's possible he disturbed a feeding group but they are generally not out there waiting to attack like piranhas."