An Australian surfer whose leg was bitten off by a shark has promised he’ll be “back in that water in no time” as he recovers from surgery.

Kai McKenzie, 23, was surfing off North Shore beach on the mid-north coast of New South Wales on Tuesday morning when a suspected three-metre great white shark bit him.

McKenzie was able to fight off the shark before catching a wave into shore, where he was treated with makeshift tourniquets before being airlifted to John Hunter hospital in Newcastle.

His severed leg washed up on shore a short time after the attack and was taken to the hospital where he underwent surgery and was recovering in a stable condition earlier this week.

McKenzie described the shark as the “biggest shark I’ve ever seen” and said the attack was “a very crazy scene and scared the living fuck out of me”, in an Instagram post on Saturday morning.

While it has not been revealed if leg reattachment surgery was attempted, McKenzie, a sponsored athlete, was optimistic about his return to surfing.

“I can tell you now if you know my personality this means fuck all. I’ll be back in that water in no time,” he wrote.

McKenzie thanked the “kind-hearted people” who had sent messages of support and donated to a GoFundMe page established to help his family with rehabilitation and medical expenses.

“To all you … legends, to anyone and everyone all your support has meant the absolute world to me. It’s so cool to see so many beautiful people support me … We are so very grateful for everything.”

The GoFundMe page has attracted more than $150,000 since it was created on Wednesday morning.

In a statement on Thursday, the McKenzie family thanked bystanders and first responders on the beach and medical staff at Port Macquarie hospital and John Hunter hospital.