SUNSET BEACH — The surf is churning as if it's doing laundry but the sun is shining, and that's all that matters on the set of the Bethany Hamilton biopic, "Soul Surfer," when the director yells action.

His cameras aren't pointed at the ocean, at least not on this afternoon. They're pointed at the beach and a crowd of cheering extras pretending they're watching a drama unfold.

"You're watching a total wipeout," director Sean McNamara said through loudspeakers as the cameras roll. "It's very bad."

Cheers die. Jaws drop.

"She's paddling and she doesn't make it and all of a sudden the wave crashes down on her," he says.

Hands cover mouths.

"Now the lifeguards are going out and she's waving them away," he said. "It makes no sense."

Gasps roll through the buff-and-bronzed extras like a stadium wave and the moment is sealed for McNamara, a heavy-set man with a braided gray ponytail, a red plastic lei and sunburned cheeks.

"Great. Cut. Genius."

On movie sets, stories come together like this — with camera magic, frantic energy and a wink — and reality depends on which way you're looking. But Hamilton's powerful life story, now being shot as a feature film on O'ahu's North Shore, doesn't need embellishment or encouragement to inspire. It has more than enough authentic drama.

Hamilton was a talented young surfer from Kaua'i who lost her left arm in 2003 when a shark rose out of the water and attacked her. She was only 13. Hamilton survived the encounter and went on to thrive as both a professional surfer and an international role model.

"Soul Surfer," which is based on her 2004 autobiography, stars AnnaSophia Robb as Hamilton. Golden Globe nominee Dennis Quaid and Academy Award winner Helen Hunt portray her parents.

ROLE'S DEMANDS

The role is demanding for Robb, a fresh-faced 16-year-old from Colorado who learned to surf after she arrived in Hawai'i last month to prepare for "Soul Surfer."

"There have been a lot of difficulties, just physically," Robb said during a break in filming. "There are challenges."

Robb, who is in just about every scene, must act with her left arm behind her back. It's painted green to allow digital special effects to erase it from the screen, but she still has to hold it there, take after take. When she paddles a surfboard, she has to use only one arm.

"When I first started, I always forgot to put my arm behind my back," she said. "Everything on land you can do with one arm. Surfing is really hard with one arm."

Despite her youth, Robb brings experience to the film. Her breakthrough came in 2005 opposite Jeff Daniels in "Because of Winn-Dixie." She went on to appear in Tim Burton's "Charlie and the Chocolate Factory" and to co-star with Dwayne Johnson in "Race to Witch Mountain."

Surfing has become a potent distraction for the young actress. She even loves the way it beats up on her — from the bruises on her hips to the purple mark on her knee that won't go away to the collisions with her board.

"I have a cut on my leg from the skeg and I love it," she said. "I hope it scars."

The young actress stood out among those being considered for the role, said Douglas Schwartz, one of four producers on "Soul Surfer."

"I felt she was a star on the rise," he said, watching Robb from under a tent. "She is a serious actress. She can pull the tears out. She has had some tearful scenes. And she has a beautiful look. She looks like a young Elizabeth Taylor."

Schwartz is best known as one of the creators of "Baywatch," the beach-and-babes series that reached 1.3 billion viewers. He said "Soul Surfer" and "Baywatch" have something in common: "Blue skies appeal."

When Robb arrived in January to prepare for the part, she flew to Kaua'i, where Hamilton lives in Hanalei, and took a few surfing lessons from the surf star. Robb's dedication impressed Hamilton.

"AnnaSophia is a really talented actress and she works hard for the roles," Hamilton said. "I didn't realize how much actors had to put into their job."

Hamilton is a regular presence on the set, watching her Hollywood family from the beach. She's serving as a consultant and plans to do some stunt surfing, although at 5-foot-10 she is a full head taller than the waifish, 5-foot-2 Robb.

"It's really weird to be having a movie made about my life," said Hamilton, now 20. "I'm not that into being famous so I think I might get more famous after this. That's been a challenge to deal with."

KEEPING IT TRUE

The film was in discussion for several years. It wasn't until the last 12 months that it seemed more of a sure thing, Hamilton says. The screenplay, which was done by McNamara, was important.

Filmmakers say they are aiming to deliver an edited film to Sony by mid-July, but no release date has been set.

"Being my own life, I want it to be as accurate as possible," she said. "But it can only be so true. We've had a few attempts at scriptwriting and this is the best one yet."

Bethany's 60-year-old father, Tom, says the filmmakers behind "Soul Surfer" have worked hard to keep his daughter's story real. But he also knows some dramatic license will be applied.

"It's a movie, not a documentary," he said. "So there are scenes that have to be developed to make a good movie. Overall, they are trying to keep it true to Bethany."

Some scenes were so real, though, he couldn't watch them being filmed.

"The day they did the actual attack and the tourniquet, I had to take a walk and I didn't come back," he said. "It was so realistic on how they re-created it. It was like living it."

The line between realism and horror may be a fine one, but the filmmakers have said they don't want to cross it. It's important, Tom Hamilton said.

"We wanted this movie to be PG," he said. "We don't want another 'Jaws' movie where kids are scared for the rest of their life."

Robb is working hard to keep it real, but as she prepares for another afternoon of acting, she said the shark attack is not the moment that will define the film. It's the emotional aftermath.

"I think spiritually, the hardest part of this film is it is a really intense story," she said. "Capturing Bethany's essence is hard to do. We have such different personalities but we were able to connect."