Swimmers, rock fishers and people in boats are being warned to stay out of the water ahead of dangerous conditions expected to hit the entire NSW coastline.
Swells of at least four metres are expected to pummel the state's coast due to the tail end of Tropical Cyclone Gita, with authorities issuing the alert for Monday and Tuesday.
NSW Surf Lifesaving spokesman Liam Howitt advised people to only go to beaches patrolled by lifeguards if they do decide to head to the water.
"Do not overestimate your ability or underestimate the conditions because things escalate very quickly in the ocean," Mr Howitt told AAP.
Bureau of Meteorology spokesman Jordan Notara says while the waves might not always be so big they will have a lot more strength.
"Deceptively large swells could occur for people on the rocks and beaches," Mr Notara told AAP.
Lifesavers rescued more than 150 people over the weekend in NSW, including 15 people in a single incident at Broulee on the state's south coast on Sunday.
Meanwhile, the search for a man has resumed after he was swept out to sea while swimming with a group of people at a Nambucca beach on the NSW mid-north coast on Saturday afternoon.
Further south, a 24-year-old man died after being dragged unconscious from the water by his girlfriend in Kempsey on Sunday.
Tropical Cyclone Gita is tracking past Lord Howe and Norfolk Islands and is expected to be an ex-tropical cyclone by the time it reaches New Zealand on Tuesday.
Australian Associated Press