A surfer being attacked by a shark in a Southland bay punched it in the face to free himself from its grip.



The 28-year-old man was on his board about 50m out from Porpoise Bay Beach, near Curio Bay, about 8.30 last night when the attack happened, police said.



Nick Smart was surfing about 100 metres away and witnessed the incident.



"He was sitting on his surfboard and the shark came up from nowhere and hit him.



"He struggled for a bit and then punched the shark and it let him go."



The man then made his own way to shore before being assisted by a doctor and a nurse, who just happened to be at the beach, Smart said.



They applied a tourniquet and gave him first aid and blankets while they waited for an ambulance to arrive.



The man was surprisingly calm throughout the entire ordeal, Smart said.



"He was totally coherent and talking.



"He was definitely in a bit of pain but he handled it really well.



"His partner was on the beach and she was right there as well so he had a lot of support."



The man's friends believed it to be a sevengill shark, although they couldn't be sure of that, and thought it was about two to three metres in length, Smart said.



An ambulance arrived about 40 minutes after the attack and transported the man to Southland Hospital, where he remained in a stable condition today.



The man was bitten three times from his thigh to his calf and there was "lots of blood", a police spokesman said.



The attack was a real shock to everyone in the Catlins area, Smart said.



"Mate, it's the first time there has ever been a shark attack in the Catlins and there has never been a shark attack in this bay.



"There's been so many dolphins in the bay over the last few days as well.



"I've spent thousands of hours in this shore break and the thought [of a shark attack] doesn't even cross my mind ... but it does now."



The attack would not put surfers off from returning to the water, with some already saying they were keen to get back out there, Smart said.



"There is no-one out there at the moment but there is people wanting to go out and there will be people out there later today."