A search for a man swept out to sea while rescuing a family member is entering a third day. 

Emergency services were called to Congo Beach about 40km south of Bateman’s Bay on the NSW south coast, following reports a man had gone missing in the water about 3.30pm on Boxing Day.

Officers were told the 19-year-old had swum out to rescue a family member experiencing difficulties in the surf.

Police said he became caught in a rip and was swept out to sea.

“They were down there fishing when the younger brothers went into the surf and this man has gone in to assist his brothers and to get them from the surf,” South Coast Police District Inspector Greg Flood told reporters.

“He has retrieved one of his brothers and I believe the other brother got out by himself and this man was swept out.”

Insp Flood urged people to swim between the flags at patrolled beaches. 

A multi-agency search including crews from PolAir, Marine Area Command, surf lifesavers, Marine Rescue NSW and the Westpac Rescue helicopter has been underway since Tuesday. 

Inspector Glenn Sullivan said three Marine Rescue NSW vessels had conducted a contour line search off Congo Beach.

“Conditions have improved offshore but the water quality is poor with a number of logs floating on the surface,” he said.