Kai McKenzie, 23, was surfing off New South Wales in Australia when he was attacked by a shark, New South Wales police said.
"Clinging to life, he was able to catch a wave back to the beach," a fundraising site set up for McKenzie said. "A retired police officer used his dog’s lead as a tourniquet to stem the bleeding before the victim could be airlifted to hospital."
Amazingly, McKenzie’s leg washed up on the beach after the attack and doctors are hoping to be able to reattach it.
McKenzie has undergone surgery and remains in critical but stable condition, according to ABC News Australia and the fundraising site.
Luke Short, who makes McKenzie’s surfboards, told ABC they had all hoped "we heard it wrong."
"It's amazing that he's survived," he added.
His surf team RAGE called McKenzie the "toughest person we know."
"Sending love to @kai_mckenzie the youngest RAGE boy on the team and the toughest person that we know," the team wrote on Instagram this week. "Yesterday he was attacked by a shark and has lost his leg while surfing in Port Macquarie. He has been through a lot breaking his back last year, he never once complained always just got on with doing what he loved as soon as possible. He is an inspiring person. The whole rage gang loves you man and we will see you soon."
Kirran Mowbray of NSW Ambulance called McKenzie "courageous" during a 7News Sydney on-air broadcast. "He turned around, caught a wave into shore."
She added that the off-duty officer "used the lead off a dog as a tourniquet to wrap around the young man’s leg and essentially saved his life."
Kevin Young, vice president of Bite Club, a shark attack survivors club, told the broadcast: "And I know he lost a leg and they packed it with ice and they’re going down to try to reattach it. That just blows my brain that that might be possible."
Port Macquarie Hastings Lifeguards later reported the beach had reopened after the attack.