WATCH: Mystery sea creatures devour meat after vicious attack on teen

WARNING, GRAPHIC CONTENT: A Melbourne father has shared a horrific video of hundreds of what are believed to be "sea lice" devouring chunks of raw meat after his teenage son was left bleeding from an ocean swim.

Sam Kanizay, 16, went for a 30 minute dip at Dendy Street Beach in Brighton on Saturday evening and walked out with what his family said were tiny marine creatures eating his legs.

His father, Jarrod Kanizay, said the creatures "ate through Sam's skin" and left him bleeding profusely.

After realising they could not stop the bleeding, the teenager was rushed to hospital where staff were baffled by the "pin-sized holes" all over his legs.

Sam Kanizay has suffered mystery injuries after dipping his feet into sea water. Photos: AAP

The following morning a curious Mr Kanizay went back down to the beach to catch a sample of the creatures he believes attacked his son.

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He place a net full of raw meat in the water and footage shows hundreds of the creatures swarming around the food.

"No one knows what the creatures are. They've called a number of people, whether it's toxicity experts or marine exerts and other medics around Melbourne at least... [and] yep, no one [knows]," he said.

Mr Kanizay went back down to the beach to catch a sample of the creatures he believes attacked his son. Photo: Sunrise

Mr Kanizay couldn't stop his son's legs bleeding and they went to hospital. Photo: 7 News/ AAP

Marine expert Michael Brown was baffled by the strange creatures and told Sunrise he believed they might be "jellyfish larvae."

"I've been doing this for coming on 20 years now and I've never seen anything like this," he said.

University of Melbourne marine biologist Professor Michael Keough said sea lice were a possibility, as "they're scavengers who'll clean up dead fish," The Age reported.

"They're mostly less than a centimetre long, and so the bites they make are pretty small, and so that's more consistent with pinprick size marks," he said.

"[They will] just be attracted to a little bit of blood. And if he's standing in the water and he's cold [he] may not notice a whole lot of little bites."

Bayside City Council confirmed to 7 News Online Dendy Street Beach will not be closed.

The teenager's father said hospital staff have no idea what the tiny sea creatures are. Photo: 7 News

Hospital staff were at a loss as to what had happened to the teenager. Photo: 7 News