Bethany Hamilton Teaches Biggest Loser Contestants to Surf
03/20/2012 AT 12:20 PM EDT
"I surprised them on the beach," Hamilton, 22, tells PEOPLE of the episode that will air March 20 at 8 p.m. ET on NBC. "They were super excited and maybe a little nervous, but I think they were just so stoked to be there."
"Getting up on the board was a bit of a challenge for them," adds Hamilton, who lost her arm in 2003 when she was attacked by a 14-foot shark. But once the contestants got the balancing element down, "Everyone managed to get up and ride some waves."
"I don't know if they were all confident that they'd be able to surf," she says. "I'm sure they had some doubts, but I think their confidence was boosted."
Hamilton was also impressed with the contestants' commitment to losing weight.
"They were getting their lives back in order and getting healthier," she says. "I think a lot of them came from the couch and all of a sudden they're in Hawaii learning how to surf. It's this shocking lifestyle change, but it's pretty exciting and they were all genuinely so happy in life right now."
As for her own way of life, Bethany hasn't let her impairment stop her from competing in her favorite sport.
"I'm surfing just about every day," she says. "I guess it's just about determination to continue doing what I love. I love being active and feeling healthy. Your days are so much better when you get out and exercise."