Avoid rock fishing and water activities on exposed beaches and rock shelves, a council spokesperson said.

''Only swim at the open patrolled beach, Lakes Beach, between the red and yellow flags," they said. 

''The hazardous conditions have been forecast to continue into Saturday before it is likely to ease later that evening and into Sunday.''

In Lake Macquarie, Redhead, Caves and Catherine Hill Bay beaches are closed.

Only Blacksmiths Beach is open.