The veteran surfer was bitten to the bone on his left foot while surfing with a friend around 8am.

He was able to paddle back to shore where he was helped by fellow surfers, who applied a tourniquet made of leg ropes, before he was treated by paramedics.

He's undergone emergency surgery at Wollongong Hospital, where he remained on Sunday in a stable condition according to a hospital spokewoman.

Windang Beach was closed Friday, but reopened on the weekend.

Surf Life Saving Illawarra duty officer Anthony Turner said additional patrols had been put on, with lifesavers in the water and on shore.

There'd been no shark sightings in the area.

"There's continual surveillance of the water by patrols on the beach, and our rescue watercraft - jet skis and inflatable rescue boats," he said.

"Our best advice is for people to swim between the flags where conditions are being monitored.

"We'd also urge people to leave the water as a precaution if they see large schools of bait fish or birds diving into the water - as the fish could attract sharks.

"We'd also advice people to avoid swimming or surfing at dawn or dusk, as sharks generally feed at that time. And avoid murky waters, especially after heavy rains."

Mr Turner also urged people to not go out in the water alone.

"Swim or surf with a buddy so if something does happen - you're caught in a rip, or concussed, or do get bitten by a shark - then you have someone there to give first aid and call emergency services," he said.

Meantime a young nipper got into trouble in the surf on Sunday morning.

Mr Turner said the 10-year-old boy, from the Helensburgh Stanwell Park club, suffered a minor head injury when he was hit by his board during a training exercise.

The boy was treated for concussion by paramedics, and taken to Wollongong Hospital.