He pictured the stranger who had disappeared under the water at Warilla Beach - a grey shadow who he had moved towards, then lost, then found again only when their bodies had collided.

He thought about what he had done to save the man, and what he might do differently should he ever face such a scenario again.

The Warilla-Barrack Point Surf Life Saving volunteer located an unconscious 25-year-old Chinese national on the ocean floor on Thursday at about 2.10pm, in unpatrolled waters more than 200 metres outside the flags.

With off-duty club volunteer Kirk Allen, Mr Pelaez brought the blue, lifeless man to the surface for retrieval by an inflatable rescue boat.

Once ashore, a circle of club volunteers surrounded the man and held his head, pumped his chest, pushed air into his mouth and zapped him with a defibrillator until his heart stirred back to life and he began to breathe again.

This, after an estimated three minutes submerged.

On Friday, the man remained in a critical but stable condition at Wollongong Hospital, having been worked on by ambulance paramedics and sedated to aid what is hoped will be a full recovery.

The Warilla-Barrack Heights club is nominating the crew involved in Thursday's events for Surf Life Saving NSW's Rescue of the Month.

Yet it is being talked about as the most significant and unlikely rescue in club history.

Mr Pelaez, a 48-year-old electrical engineer from Dapto, is an atypical poster boy for lifesaving heroism, having only joined Warilla-Barrack Point club 12 months ago as a way of busying himself now that his children are getting older.

His 18-year-old son David, who also joined the club, was at Warilla Beach on his first patrol when Mr Pelaez went into the water on Thursday.

In his training, Mr Pelaez learnt that he should search the ocean from above, looking down from an inflatable rescue boat.

But when a fisherman raised the alarm on Thursday, other volunteers went to get the boat while Mr Peleaz went into the water and - drawing on techniques he learnt scuba diving as a younger man - began searching.

He swam down low, with his belly close to the ocean floor, in the section of water the fisherman had indicated.

His mind, he later told the Mercury, was "completely blank".

"I started to go in circles," he said. "I think it was my second time around when I saw a grey object in the distance.

"You can't see much with your eyes open under water. I made a beeline for him, and I pretty much swam right on top of him."

Club president Alan Beveridge said some debriefing had occurred in the aftermath of the rescue but the club would further dissect events to fine-tune its procedures.

He said a variety of factors had combined to swing the rescue in the man's favour - including the close proximity of a set of flippers and other equipment used by rescuers, the speed of the rescue boat, the presence of the off-duty Mr Allen.

"Everything came together," said Mr Beveridge, who helped to collect the rescue boat and pushed air into the man's mouth once he was on shore.

"[Mr Pelaez] has only been with us a short amount of time but he's a good listener and he's always keen to learn.

"I would rate this as very high teamwork."

Club members felt emotionally drained by the events, he said, and were keen for word of a good outcome at Wollongong Hospital.

Unconfirmed reports suggest the stricken man went into the water to retrieve a ball in the moments before he found himself in trouble.

*Contrary to earlier reports, the rescued man is aged 25, not 23," according to a health service spokeswoman.