The break walls lining the exit to Narooma bar on the NSW South Coast were crowded with around 50 people who had ventured out to watch the eight to 10 foot swell as it pounded into the rocks at 11am on January 5.

Among them was Kyle Abel and his family, on holidays visiting friends in Narooma from their home in Queanbeyan in NSW's south east.

Mr Abel had decided not to go to the beach that day because of the terrible weather and huge swells. Yet as he walked along the break wall with his family, he saw a fishing charter boat trying to pierce through the waves.

"They were absolutely crazy going out on a day like that," Mr Abel said.

"Exactly what I thought would happen happened: A big clean-out set came through. The boat hit it and a guy was dragged off the back."

A man in his 50s was thrown off the back of the boat and left stranded in the water.

A smaller boat nearby tried to come to the rescue, but kept stalling. Mr Abel feared it may crash into the break wall and cause a bigger disaster.

The keen surfer and spear fisherman had been out in similar sized swells before.

"If I hadn't been in a surf that big before I wouldn't have gone," he said.

"I was hesitant. I didn't want to need to be rescued myself or drown in front of my kids."

He grabbed his bodyboard, wetsuit and flippers from his car.

"If it wasn't for those I wouldn't have gone out," he said.

"You wouldn't have the strength to swim against a surf that big."

By now, the overboard man had drifted to the north and was closer to the beach, where it would be more difficult for any rescue boat to reach him.

"I didn't want to gamble on [leaving him there for someone else to rescue]," he said.

"I knew I had to do something."

To the surprise of many onlookers, Mr Abel entered the water and swam to the man.

"He went to clamber on to me, but I told him to hold his vest and keep breathing," he said.

Mr Abel then began towing the man towards the shore, pulling him behind on the bodyboard.

"I had to let go of him at times, and go back under because we were getting hit by massive waves," he said.

"I'd come back up and grab back onto him and tell him to keep kicking."

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The strong tides swept the pair into a gutter where a strong rip carried them towards the break wall.

Mr Abel directed them towards a calmer section of water, where they were able to more safely approach the break wall.

Bystanders helped drag the man onto the rocks with Mr Abel pushing from below.

The man splayed exhausted onto the rocks, where ambulance services were soon able to check the man.

"My legs were like jelly," Mr Abel said.

An onlooker told him the entire rescue took 25 minutes.

"The term 'hero' is pretty funny," Mr Abel said. "I'm not really a hero, I just had the ability and was in the right place at the right time."