A surfer mauled by a ‘monster’ Great White shark on South Australia’s west coast is fighting for his life in hospital.

The surfer, named as Chris Blowes, 26, was about 350 yards offshore at Fishery Bay in Port Lincoln National Park.

Shocked witnesses saw an 18 foot great white shark swimming away with the surfer’s leg and a surfboard in its jaw.

He was among a group of about a dozen surfers in the water about 9.45am when the shark struck.

Fellow surfer Glenn Lugg had just exited the water when he saw what he described as a "massive" great white shark, he estimated to be about 6m in length.

Shark: Fishery Bay, where the incident happened (
Image:
7 News)

The shark came in and bit his leg off and the guys helped him in and carried him up the cliff,” Mr Lugg, a surfer of 25 years, told Adelaide Now .

He said the surfers were only 4m from the rocks at an area known as right point.

The shark victim was taken to hospital before being airlifted to Adelaide for further treatment.

Savage: A great white shark. File picture (
Image:
Getty)

"There was blood everywhere," another witness said.

The attacked happened during conditions that police and marine experts have previously said are dangerous.

The overcast conditions make it difficult for surfers to see sharks that might be in the area and it is believed that sharks often mistake humans for seals or dolphins.