Crews stood down in search for swimmer missing since Sunday

Police confirmed Marine Area Command officers in boats and on jet skis had been stood down.

Local police will still carry out searches of the area off Stockton Beach, where a young man was last seen submerged in water about 200 metres offshore on Sunday afternoon.

Emergency services - including the Westpac Rescue Helicopter, Marine Rescue NSW crews, police and surf lifesavers - spent three days scouring the coast for any sign of the swimmer.

He sadly remained missing on Wednesday night and the additional resources were called off late on Tuesday, police told the Newcastle Herald.

The missing swimmer, believed to be a man of Middle Eastern appearance 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.

Weather conditions significantly deteriorated on Wednesday when thunderstorms and heavy rain lashed the Newcastle area.