Swimmer missing for 24 hours, crews scour beach from sea and sky

Police and surf lifesavers on jet skis were joined by Marine Rescue NSW crews and police vessels on the coast off Williamtown, between Stockton and Anna Bay, during the operation.

The Westpac Rescue Helicopter joined the search and was seen circling the Stockton beach area.

At least three jet ski crews - from Surf Lifesaving NSW and the NSW Police force's marine command - were part of the search effort from about 8am.

Three Marine Rescue NSW boats, alongside a police vessel - were conducting parallel line searches off Stockton beach.

"With swells ranging from 1 to 1.5 metres and light winds, sea conditions are currently favourable," Marine Rescue NSW Inspector Courtney Greenslade said at the time.

The missing swimmer, believed to be a man of Middle Eastern background aged between 18 and 20, has been unaccounted for in the sea since about 3pm on Sunday.

He was last seen by his friends becoming submerged in water about 200 metres offshore, near the four-wheel-drive beach entry point off Lavis Lane at Williamtown.

Police raised the alarm with surf lifesavers at Stockton and Birubi after calls for help came in.

Five people were reportedly caught in a rip.

Four managed to make it back to shore on their own but the fifth man did not return.

The search was called off temporarily at about 3.30pm yesterday.

A NSW Police spokesperson confirmed the operation would resume with the same resources - including officers on jet skis and marine area command officers - at 8am today.

Meanwhile, the Bureau of Meteorology has forecast a high chance of rain and a possible thunderstorm for the next two days in Port Stephens

Up to 10mm of rain could fall today and up to 25mm on Wednesday.

It should be mostly sunny on Thursday and Friday with the chance of showers on Saturday (8mm) and Sunday (3mm)

Maitland could get up to 20mm today and 40mm tomorrow, with storms possible on both days.