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.

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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.

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.

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

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