A surfer is in a serious condition after suffering deep lacerations to his leg in a shark attack at Nambucca Heads on the New South Wales mid north coast.

Father of three Joel Mason, 36, was surfing at a break locals call "The Bar" — where the Nambucca River flows into the ocean — when the attack happened about 7:00am yesterday.

Witnesses say the man was just about to catch a wave when a nearby pod of dolphins came through the area and the attack occurred.

"He just disappeared," a local man watching from the shore, who did not want his name used, said.

"I saw him [the attack victim] out there and was watching the pod of dolphins and the waves and my dogs and then just lost sight of him.

"I thought he couldn't have come in that quick."

Nambucca Heads on the New South Wales mid north coast

A spokesperson for Surf Life Saving NSW, Donna Wishart, said three or four surfers were in the water at the time of the attack.

"One of them has seen him disappear under the water, with a flume of water spraying up and then the victim has lifted his arm up to indicate he was having a problem," she said.

The surfers dragged the man up onto the rocks of the breakwall where a long-standing member of the Nambucca Heads Surf Lifesaving Club applied a tourniquet which paramedics said saved his life.

NSW Ambulance Chief Inspector Brian Parsell said the man suffered five deep lacerations to his lower leg.

Chief Inspector Parsell said the man lost "a fair amount of blood" in the attack and received a blood transfusion at the scene before being airlifted to John Hunter Hospital.

However, paramedics at the scene said he was calm and very "stoic" when being treated.

The helicopter crew were going to stop en route at Port Macquarie to pick up more blood products, Chief Inspector Parsell said.

"The most important priority for this gentleman is to stabilise the bleeding, get that under control as best we can, but what we do know is he needs to be rushed to theatres on arrival at John Hunter Hospital," he said.

The attacked happened at the river mouth. ( Flikr: Ken Hodge )

A spokeswoman from the NSW Department of Primary Industries said authorities were not sure what type of shark was responsible for the attack.

She said the man's injuries would be inspected to help determine the species.

Beaches in the area were closed and extra aerial and jet ski patrols were conducted.

Surfer previously attacked at same break

The attack brought back memories for local Richard Ellis, who was bitten by a shark at the same surfing spot in 2001.

"It certainly brings a feeling of uncomfortability," he said.

"There's nothing good about a chopper hovering over our local surf break."

Mr Ellis said his attack was similar to the one that occurred on Sunday. Both men were surfing in a break locals call The Bar, where the Nambucca River flows into the ocean, and both suffered serious leg injuries.

"It's possible mistaken identity, there was fish around at the time, and dolphins around," he said.

"But there's still some randomness to it, it was a different time of year and different circumstance altogether, so the commonality is that people still go surfing out at these places regardless."

Mr Ellis said sharks were simply a known risk for surfers.

"The reality is the frequency of attacks is still pretty low and the frequency of fatalities is really low and it's still proportionately a low-risk activity and there's a lot of pleasure that comes with it," he said.