Baited breath?

SYDNEY: Freedivers will literally be holding their breath today as a daredevil world first is attempted off the northern NSW coast.

Mike Wells, 39, a 19-year veteran of freediving (the art of diving without oxygen tanks) will swim through Fish Rock Cave said to be Australia's longest ocean cave on a single breath.

Nobody has completed a freedive through the 120m structure.

On top of the risk of swimming through such a confined space for around three minutes, the water around Fish Rock Cave, 2km off the South West Rocks coast, is shark infested.

"Apart from being in a tunnel, sharks are the biggest risk, for sure," Wells said.

"I've dived down there before and I actually get to recognise some of the sharks, I recognise their markings and know them individually.

"Hopefully they'll recognise me and let me get on with it."

- AAP