Despite losing most of his leg in a shark attack in Hawaii, a 25-year-old surfer says he is determined to ride the waves once again.

Colin Cook was attacked by a 10-to-12-foot tiger shark in Oahu's North Shore on Friday. Following the attack, doctors amputated most of his left leg. However, by the next day, he was already out of his hospital bed and taking a few steps, Hawaii News Now reports. He took even more steps on Sunday.

According to Cook's father, Glenn, "the tiger shark came out of nowhere. It grabbed his left leg and pulled him under and he grabbed the board with one hand, but the shark started pulling him backwards in the water," he said.

"He was able to pop up ... and with his left hand, he pushed back on the shark which gave him tremendous injuries on his hand, but with his right hand he was able to punch the living heck out of the shark's nose."

After Cook was pulled to shore, a quick thinking bystander used a surfboard leash as a tourniquet to help stop the bleeding, which doctors say saved his life.

"It was his left leg that got taken, and then it was his left hand that he lost a couple of his fingertips on," said Cook's cousin, Chris Webster, to CBS affiliate WGMB. "So I imagine he was holding the shark off while he was punching it."

Now the Oahu surfer says he looks forward to returning to his fiberglass surfboard shop, which he had just opened, and getting back in the ocean. According to his father, Glenn Cook, Colin hopes to be surfing and running his shop again by the new year.

Until he is able to walk and work again, Cook's high school friends have started a GoFundMe page to raise $50,000 to help Cook manage his expenses during his recovery. So far, they have raised more than $17,000.

"People from all over the world now are donating and people have no idea who Colin is. That's why it's important to tell Colin's story, this isn't about a shark attack. This is about a community, a surf community embracing Colin Cook and his passion for the industry," said Glenn.