After shaking off what he thought was sand coated around his ankles, he walked across the beach before looking down and realising that his feet were "covered in blood".
Sixteen-year-old Sam Kanizay from Brighton Beach, Melbourne had just come home from playing football and his legs were exhausted and very sore after all that exercise. "It sort of looked like hundreds of little pin holes, or pin type bites, distributed all over my ankle and the top of my foot".
Two hospitals in the area were unable to ID what caused the attack, so Kanizay's father made a decision to go back to the beach and investigate himself.
Marine biologists have said they were likely to have been sea fleas, tiny scavenging marine animals.
But when he got out of the sea he discovered he was bleeding profusely from the calves down.
Kanizay adds,"If it is sea lice, then it is a pretty dramatic example of it" he'd already been suspicious about the journey to the beach, once a friend had broken up with blood loss feet a couple of weeks before.
When he went home, Kanizay tried to wash off the blood, but the bleeding did not stop.
Investigating on his own, Jarrod Kanizay put on two wetsuits, returned to where his son had soaked his feet and used some raw meat to lure the unknown pests into a pool net. His father Jarrod Kanizay said it "looked like a war injury...like a grenade attack".
He said: "What is really clear is these little things really love meat".
Associate Professor at Monash University's School of Biological Sciences Richard Reina, however, was confident Sam's bites were caused by sea fleas.
Sam, 16, continues his recovery at Dandenong Hospital after doctors struggled for most of Sunday to control the bleeding.
The footage shows the intensity at which the creatures devoured the flesh - mirroring the appetite they demonstrated with 16-year-old Sam.
According to the Alaska state Department of Fish and Game, sea lice are small, oval-shaped crustaceans that are often seen hanging on to salmon - they are parasites.
Kanizay is expected to be just fine, but remained at the hospital for observation.
Reina told news.com.au that sea lice don't generally travel in a large group, but that once a small number drew blood, it would have attracted all the others.
Marine biologist Genefor Walker-Smith examined a sample collected by Jarrod and said the creatures are naturally-occurring scavengers, which commonly bite, but do not usually cause these kind of injuries.
They see sting rays "every day, either lying on the bottom or swimming underneath us".