Bethany Hamilton (AnnaSophia Robb) is a teenager who lives in Kauai, Hawaii who loves surfing. One day, she and her best friend Alana Blanchard (Lorraine Nicholson) go surfing with Alana's father and brother. As Bethany dangles her left arm in the water, a tiger shark appears out of nowhere and bites off her arm near the shoulder.Alana's father puts a tourniquet on Bethany while Alana's brother calls 9-1-1. An ambulance meets them on the way to the hospital.The family, however, bears no ill will towards Alana's family for taking her out to the place where she was attacked. After a recuperation period, Bethany gets back in the water and learns to surf with one arm, eventually re-entering competition. She tells her rival Malina not to take it easy on her, and rejects a five-minute head start offered by the judges. She doesn't perform well because she can't stay on the board long enough to go out and catch a competitive wave, and loses. Disheartened, she decides to give up competitive surfing.She sees the 2004 Indian Ocean earthquake and tsunami on television, which places her own problems in perspective. She decides to join her youth group on a missionary trip to help the devastated people of Phucket, Thailand. The people are understandably afraid of the water, including a little boy. Bethany decides to go into the water with a surf board, hoping this will coax the boy into the water. It works, and the realization she can use her gift to inspire people motivates her to take up surfing again.Tom rigs a handle on her surfboard which she can use to prevent falling off while paddling out to the waves. She enters the regional championship, thanks her rival for treating her as a serious competitor, and performs respectably, though she is still chasing third place.With only minutes left on the clock, the waves die down and all the surfers can only loiter, waiting for them to start back up. Bethany is the only one to sense a big wave forming, and she alone paddles out. When it forms, the others can't get out in time and she catches it just as the horn sounds. She will win if it was in time, but the judges rule that the time has expired. Malina is the winner, but she has finally gotten over her differences with her, inviting her up on the platform to share first place.Subsequently, Bethany lets the reporters interview her. One asks her what she would do if given the chance to undo the loss of her arm. She says that she would still lose it because she can embrace more people now than she ever could with two arms.