A rescue operation was launched after a boat overturned off Little Marley Beach in the Royal National Park.
A Westpac Life Saver Rescue Helicopter attended the scene about 1.30pm.
A helicopter crew officer was winched down to check on the condition of the patient who had managed to make it to shore after his boat flipped.
The patient, a man in his 50s, was treated and handed over to NSW Ambulance teams on the beach in a stable condition for transport to Sutherland Hospital for observation
It is the second boating mishap in the region this week.
A rope wrapped around the propeller may have caused a sailing boat to capsize off Boat Harbour, Kurnell, leading to the death of a man, 72, on Monday.
The fouled propeller became apparent when the stricken vessel was fully exposed on the beach at low tide.
Read more: Fouled propeller on stricken boat
