A group of surfers and an off-duty doctor have been praised for their attempts to save a man who drowned in "relatively calm" conditions at a beach just south of Sydney.

Paramedics were called to Stanwell Park Beach, north of Wollongong, about 1:40pm after receiving reports a man was seen floating in the water.

Surf Life Saving New South Wales said the man, believed to be an Indian national, had been swimming outside patrol flags with two friends at the northern end of the beach when he got into difficulty.

Five surfers pulled the unconscious man across several surfboards before attempting to perform CPR.

Lifesavers in an inflatable boat travelled 800 metres to the scene while four ambulances and a rescue helicopter were deployed.

An off-duty doctor also joined in the resuscitation effort, however the 24-year-old man could not be revived.

Conditions on the water at the time of the incident had been described as "relatively calm", surf life savers said.

But NSW Ambulance Inspector Matthew Sterling said the coastline along the area was "notorious for its rips".

He said two of the man's friends were taken to Wollongong Hospital for shock.

"Obviously they were quite distraught," he said.

Surf Life Saving NSW chief executive Steven Pearce praised everyone involved in the rescue attempt.

"Everyone from the surfers who had the presence of mind to notice the swimmer's difficulties and get him out of the water through to our wonderful volunteers and emergency responders reacted in a professional and compassionate manner," he said.

"This is a tragic incident coming so soon after the opening of the 2018/19 patrol season, and our thoughts are with the family and friends of the young man at this sad time."

A report will be prepared for the coroner.