Search called off for missing NSW swimmer

The search for a man seen floating in "treacherous" conditions off Sydney's northern beaches has been called off after nobody came forward to report a missing person.

Rescue helicopters, lifeguards and emergency service workers had searched Turimetta beach near Warriewood after witnesses reported spotting a male swimmer in trouble on Thursday afternoon amid dangerous surf conditions.

The search resumed at 7am on Friday but was stood down by police within hours, a Surf Life Saving NSW spokesman told AAP.

"There's no traces of a body, no person reported missing, so the search has concluded," a NSW police spokesman told AAP.