A police officer shows the surfboard with a bite mark after the attack.
The mate of a surfer who was attacked by a shark this morning has described the frenzied scene as the incident unfolded.
The flatmate of a man who survived a shark attack after being bitten on the leg on the NSW far-north coast has described the frenzied scene as the incident occured.
The 41-year-old man was surfing near Belongil Beach, north of Byron Bay, about 6.40am on Sunday when he was bitten on the leg, police said in a statement.
The surfer managed to fend off the shark and swim to shore while clinging to his surf board. Members of the public tried to treat the man while they waited for emergency services to arrive.
The man, who lives in nearby Suffolk Park, sustained injuries to his upper thigh.
He then returned to shore on his board and alerted other surfers before he was airlifted to Gold Coast University Hospital in a serious but stable condition.
His flatmate, Dane Davidson, told media the pair had just entered the water and were paddling out when the shark - believed to be a baby Great White - struck.
"Keen for a wave this morning, went for a surf and had literally only just paddled out of the water," he said.
"I was about 20 metres behind him (the victim), he sat up on his board and instantly a shark smashed up from underneath and knocked him clean off his board.
"There was a lot of thrashing and splashing. He started screaming, we didn't realise until we paddled back to the beach that there was a big chunk taken out of his leg.
"There was a lot of blood, a lot of bleeding. The bleeding was pretty bad. We didn't see the shark but a bloke who was out there earlier said he saw a fin and he reckons it was a juvenile Great White."
The attack has prompted surf life saving crews to patrol beaches around Byron Bay, sweeping areas on jetski notifying the public of the risk of swimming.
According to The Northern Star, four ambulance crews rushed to the man for treatment before being transported by the Westpac Rescue Helicopter service.
Belongil Beach and Main Beach have been closed for 24-hours.
It is not confirmed what species of shark attacked the man.
Beachgoers are urged to follow safety advice from Surf Life Saving NSW and by visiting the Department of Primary Industry's website www.dpi.nsw.gov.au/sharks and the SharkSmart app.