A frantic search for a yachtsman missing - feared drowned - in dangerous seas on the NSW Mid North Coast has been suspended amid wild weather.
The man was washed off his vessel after a huge wave struck the yacht near Broughton Island on Wednesday afternoon.
Westpac Rescue Helicopter.
A rescue helicopter has been dispatched to search for the man, aged in his 60s, as the boat's remaining crew made their way back to Port Stephens.
He was last seen in water about two nautical miles north of Broughton Island, about 14km north-east of Port Stephens.
The Westpac chopper was also called to help search the waters off Broughton Island as rough seas were churned up by the low pressure system.
Rescue crews were also battling to reach at least 21 people stranded at a camping ground on NSW's south coast amid rising floodwaters.
Hunter Westpac rescue helicopter crewman Graham Nickisson said the bad conditions were deteriorating.
"The conditions are some of the worst for this sort of search and rescue operation," Mr Nickisson said.
"The visibility is extremely poor and the seas are huge."
Port Stephens Marine Rescue unit commander Tony O'Donnell said that early reports indicated that the man was swept overboard in heavy seas.
"Details are very sketchy ... a call came in at about 11.45am reporting a man had been swept overboard from a 36ft yacht in rough seas north east of Broughton Island," Mr O'Donnell said.
"Both the water police vessel and rescue helicopter have responded to the distress call. There are no reports of damage to the vessel."
Mr O'Donnell said the unit's Danial Thain had also been called out to tow in another distressed vessel east of Port Stephens.
It is understood the passengers on board are not in any danger.
The east coast low, which is sitting off the coast of Port Stephens, has created massive swells.
The unprecedented wet weather has also made it difficult for helicopter rescue crews to reach the group of 16 adults and five children who've been isolated at the Bendethera Valley campground west of Moruya since Sunday.
National Parks rangers are with the group which has adequate food and water for at least two days, SES spokeswoman Jacqueline Rose said.
Fairfax Media
With AAP