A 25-year-old fisherman who swam nearly eight kilometres to shore without a life jacket after he was knocked off his boat is lucky, say locals, who saw several sharks feeding in the area.

The man's empty boat was found with the engine running off Kirra Beach about 5.15pm yesterday, nearly six hours after he left Tweed Heads to go fishing at Nine Mile Reef, about six kilometres from shore.

Police believe he was knocked off the boat at the reef and, with the motor running, it drifted away.

The man then began swimming towards the shore, police said.

Queensland police began an air and land search, which was postponed at 9pm.

The man was found at Fingal Head, about 7.5 kilometres from Nine Mile Reef, at 10.30pm and was taken to Tweed Heads Hospital with cuts and mild hypothermia.