Surf Life Saving NSW's Manager of Lifeguard Services, Steve Leahy, was driving near Lady Robinsons Beach when he noticed a man slumped over his sailboard at 5.30pm.

The sailboard's mast had snapped and the man had become exhausted trying to paddle to shore.

Mr Leahy stopped and called the SLSNSW Duty Officer and Botany Bay Water Police, but no boats were available so contacted the Westpac Lifesaver Rescue Helicopter, which arrived a short time later.

The helicopter crew lowered a rescue crewman into the water, rescued the man and the crewman paddled the board back to shore at Brighton-Le-Sands.

Mr Leahy said the man was exhausted, but extremely grateful to be back on dry land.

He declined to be taken to hospital.