Police say two men, aged 29 and 30, were on board the vessel when it overturned off Seven Mile Beach about 11.30am. 

The vessel overturned in strong, north-easterly winds. While one man was able to cling to the upturned vessel, the other drifted away.

The men let off two marine flares.

Members of the public observed the flares and contacted emergency services.

Water Police, as well as Shoalhaven Marine Rescue, and the Ambulance Rescue Helicopter attended and located the men.

They were taken ashore and assessed by NSW Ambulance paramedics. They were uninjured.

The catamaran has not been recovered at at 4pm.

Earlier 

1.40pm: A second person overboard has been picked up by Marine Rescue. 

NSW Ambulance paramedics are awaiting their return to shore. 

1.35pm: The person overboard has been picked up by a windsurfer and been brought back to shore. 

1.25pm: An ambulance rescue chopper is en route to Gerroa, where two flares were reportedly set off out at sea a short time ago. 

Intial reports indicate a person has fallen off a catamaran. 

The flares came from a vessel 500 metres off shore. 

A Marine Rescue vessel is searching the waters. A police command post has been set up at Black Head Reserve. 

More to come