Despite the attack, Hamilton, 19, has proved she could still compete with the best of them, jumping right back in the water one month later.
"To me, it's like never getting in a car because you're afraid of a collision. Not surfing doesn't work for me," she said.
On the professional surfing circuit, the Kauai native has become known for her courage, positive attitude and fierce competitive spirit.
"One arm might handicap me a little in competition, but I just work with what changes I know I have to make, and I'm pretty used to it now," she told ABC News. "It mainly depends on the wave conditions...I only get half the waves everyone else rides, so mine have to be good!"
Hamilton first told her story to "20/20" after the October 2003 attack. Many doubted if Hamilton -- then 13 years old -- would ever be able to surf competitively again, but she refused to let her story end in tragedy.
"I get tons of letters...people saw that I didn't give up on my dreams," she told "20/20" in a November 2003 interview. "I kept surfing -- it helped them out a lot and that just shows that good can come out of bad stuff like this."
It's no wonder then that Hamilton's biggest challenge and the incident that propelled her to national fame happened in the water. Born into a family of surfers, Hamilton had been catching waves and trophies since the age of 8 before her harrowing attack.
Suzanne "Bobo" Bollins, a fellow surfer and long-time family friend, says she always knew Hamilton had what it takes to be a champion.
"I consider her a little ocean person. I'd say she has salt in her blood," Bollins said. "She lives and breathes the ocean. She gets the big waves. She doesn't mess around...I have said to myself, 'There's the next world champion.'"
On Oct. 31, 2003, the water was glassy and calm at Hamilton's favorite surf spot, known as "The Tunnels," when her life changed forever.
"I was laying on my board sideways. And then...the shark came up and grabbed a hold of my arm," she told "20/20."
"And then, I was holding onto my board, with my thumb, because I probably didn't want to get pulled under. It was like pulling me back and forth, not like pulling me underwater. Just like, you know how you eat a piece of steak?... It was kind of like that. And then it let go. And then went under. Then I looked down at the water, and it was like really red, from all the blood in the water."
It happened so quickly that none of the surfers around her ever saw the creature or her struggle with it. But, the attack severed her left arm just below the shoulder.
"I think I figured out that if I panicked, then things wouldn't go as good as if I was calm," she said.
"I was praying to God to rescue me and help me," Hamilton said. "And then, I had this one pretty funny thought, I think. I was thinking, 'I wonder if I'm going to lose my sponsor.'"
The shark took a 16-inch bite out of her board and Hamilton nearly died from blood loss.
"When I first saw her in the hospital that morning she looked really pale but she had a brightness in her eyes that I could just say, 'You know, she's going to be alright,'" Bethany's mother, Sherry Hamilton told ESPN.