Missing swimmer sparks search at popular Sydney beach

A search will resume today for a swimmer who went missing at Sydney's popular Bronte Beach.

Police, ambulance, crews, surf life savers and a NSW Ambulance helicopter crew all searched into the night but didn't find any trace of the man, who disappeared at about 7.45pm yesterday.

Surf Life Saving NSW city branch duty officer John Restuccia said two friends were swimming. When one of the men didn't return to the beach, it sparked a search operation on the beach, in the water and with a helicopter above.

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He said crews searched the rocks as far south as Bronte Bogey Hole, near the baths, and would resume again at 6.30am today.

"There's only one safety message that surf life saving has, it's swim between the flags at all times, swim at a patrolled beach at all times," Restuccia told 9News.

"If the flags are down, there's surf life savers or lifeguards, you don't swim at all."

State Emergency Service volunteers earlier rescued two people stranded at Penrith Beach, who'd been swept to the other side of the lake and were not injured.