NSW surfer dubbed hero after boat rescue

A Sydney schoolteacher is being hailed as a hero after he freed a fisherman from a capsized vessel during an afternoon surf.

Chris Noble finished work early on Friday and thought he'd catch a leisurely wave or two before heading out for the evening.

In the end he caught three - but not before risking his life to help rescue four boaties whose five-metre runabout capsized in waters off La Perouse, in Sydney's southeast.

"It it didn't prove as relaxing as I was anticipating," the 30-year-old joked on Saturday.

Among the group was a 27-year-old Roselands man who became trapped in the upturned boat's cabin and survived for several minutes under the water tanks due to an air pocket.

Mr Noble says he was paddling out to the break near Bare Island when he saw a large wave coming down and the boat pitched at a dangerous angle.

Suddenly, three men were in the ocean.

"'Help my mate, he can't swim'," Mr Noble remembered one calling out to him.

He had just hauled the non-swimmer onto his board, when the first man again yelled for help.

"He screamed out, 'My mate's still in the cabin' - and by that stage the boat had already gone down," Mr Noble recalled on Saturday.

He told how he dived under the water and felt his way forward to unlock the hatch at the front of the boat, urging the man inside to get himself to the opening if he could.

"He was able to, thankfully. He was pretty white," he said.

Mr Noble stayed with the men until help arrived.

Police have dubbed him a hero and want to see him formally recognised.

"If he wasn't there and he didn't do what he did, someone could have lost their life," Sergeant John Cox said.

He said the fishermen appeared to have ignored warnings in a patch notorious for flipping boats.

"They shouldn't have gone in that close to rocks - there's a marker out there to tell you to go out wider," Sergeant Cox said.

"They've just taken the risk and it's caught them out, unfortunately.

The fishermen are yet to speak to police.