On Octover 31, 2007, Hamilton went for a morning surf along Tunnels Beach, Kuai with friend Alana Blanchard along with Blanchard’s father and brother. Around 7:30 a.m., she was lying sideways on her surfboard with her left arm dangling in the water, when a 15 ft tiger shark attacked her, ripping her left arm off just below the shoulder. If the shark had bitten two inches further in, the attack would have been fatal. Hamilton had lost almost 60% of her blood that morning.
Despite the trauma of the incident, Hamilton was determined to return to surfing. Less than one month after the incident, she returned to her board and went surfing again. Initially, she adopted a custom-made board that was longer and slightly thicker which made it easier to paddle. She has observed that she has to kick a lot more to make up for the loss of her left arm. After teaching herself to surf with one arm, she has again begun surfing competitively. She is now back to using competitive performance short-boards again.