Rangers are searching for a small crocodile that bit a man on the shoulder while he was snorkelling in Queensland's far north.

The Environmental Protection Agency says the man was snorkelling off Lizard Island, north of Cairns, on Sunday afternoon when a crocodile attacked him.

EPA wildlife management director Nick Rigby said the man was not seriously hurt.

"I understand the man's stinger suit was torn. His skin was not punctured and he sustained a small red mark on his arm which was treated with antiseptic," Mr Rigby said.

"If the animal can be caught, it will be removed from the area."

He said the EPA was also investigating sightings of a 1.8m crocodile at nearby Anchor Bay.

Mr Rigby said north Queensland, including offshore islands, was crocodile habitat and at this time of year with the wet season in full swing, the animals were more active.

"People need to take responsibility for their own safety and remain cautious when involved in activities on or near the water," he said.