The man received five deep lacerations to one of his lower legs when he was bitten by a shark at Nambucca Heads after 7am on Sunday, a NSW Ambulance spokesman said.

Joel Mason, 36, managed to swim to a nearby breakwall, where a passerby saw him and contacted emergency services.

He was treated at the scene before being flown to John Hunter Hospital in Newcastle, where he's in a stable condition.

Mr Mason's father, Rob, told Nine News his son has loved surfing since he was young and it was "very disturbing" when he found out about the incident.

"He's surfed since he was five or six years old," Mr Mason said.

"He loves to surf early and he loves to surf by himself which is sort of a bit risky.

"He says he's shark bait but he's prepared to take the risk and he does."

NSW Ambulance spokesman Steve Fraser said Mr Mason remained "extremely calm, extremely stoic" throughout the ordeal.

With AAP