An Australian man whose leg was bitten off by a Great White shark remains in critical condition at the Royal Adelaide Hospital.

On 25 April, Chris Blowes, 26, was surfing at Fishery Bay, a popular surfing and swimming spot about 40km (12.2 miles) south of Port Lincoln. The attack occurred at 9:45am local time, 350m offshore as Blowes was surfing in a group of about 12 people.

Horrified witnesses estimated the shark to be 6m long and said they saw the animal swim away with Blowes' leg and the surfboard in its powerful jaws.

"The shark came in and bit his leg off and the guys helped him in and carried him up the cliff," said Glenn Lugg, who has surfed for 25 years in the area.

"I was just watching the shark go out to the ocean with his board still attached. Obviously the shark still had his leg and he was still swimming around with it," Lugg told Adelaide Now.

"There was blood everywhere," another witness said.

Family's thanks

Fellow surfers scrambled to rescue the victim from the water, who was rushed to Port Lincoln hospital with life-threatening injuries. Blowes was airlifted to Adelaide Hospital for further treatment.

The victim's family has thanked well-wishers and all those who helped in a statement.

"Currently our sole focus is on our unified, unconditional support and belief towards Christopher's big fight he has ahead, and we ask that our privacy in being able to provide that is respected at this time," the statement said.

"From the bottom of our hearts we wish to thank his inspirational mates who rescued him and got him to safety and all of the wonderful medical professionals both here in Adelaide and in Port Lincoln who have attended to Christopher."

The Mayor of the District Council of Lower Eyre Peninsula, Julie Low labelled said: "It's a beautiful place and it's such a shame this has happened".

"Our sympathy goes out to the victim, and his family and friends."