Huge waves are pummelling beaches and the Wollongong breakwall on Saturday, with a hazardous surf warning for most of the NSW coast in place until midnight.
The swell is being generated from Ex-Tropical Cyclone Uesi with offshore rescue boats based in Kiama, Sydney and Ballina on standby to respond to any critical coastal incidents.
Surf Life Saving NSW lifesaving director Joel Wiseman has urged "members of the public not to engage in risky coastal activities".
"If people don't heed emergency service warnings and put themselves in danger in these extreme conditions, it's possible that lifesavers will not be able to save them."
With damaging sea swell forecast in many locations, there is a threat of coastal inundation and erosion in low-lying areas.
Large tidal surges are a possibility in some areas which will exacerbate the damage caused by the extreme weather event last weekend.