No sign of British tourist missing off Sydney's northern beaches

Lifesavers have closed the northern Sydney beach where a British man went missing while swimming last night.

The 31-year-old hasn't been seen since he entered the water at South Curl Curl alone at about 7pm after fishing with a friend, police say.

The friend raised the alarm when he didn't return, sparking a search of the area.

Boats and jetskis were launched this morning as foot patrols continued with the Lifesaver Rescue helicopter also joining the effort.

Surf Life Saving NSW spokesman Keiran Menzies said there had been no sightings of the man or any of his belongings in the surf.

He said it was hard to say how the man would have fared in the water overnight.

"It's all dependent on the conditions on the day and their competency as a swimmer," he said. 

Current conditions were choppy, but not severe, he said.

Nevertheless, he said the North and South Curl Curl beaches have been closed as rescue personnel swept the area.

A command post has been established near the South Curl Curl Surf Club.

The dive unit has also been recruited for the search.