“Soul Surfer” is an earnest family movie that practically drowns in uplift and good intentions. A fact-based tale of a young surfer who loses an arm in a shark attack but pluckily continues in the sport, the picture, with its insistently Christian subtext, will certainly appeal to the Sunday school crowd, but is likely to strike others as cloying and shallow.

Blonde AnnaSophia Robb, who looks great in a bikini, stars as Bethany Hamilton, the spunky daughter of Tom (Dennis Quaid) and Cheri (Helen Hunt). Along with Beth’s two jovially roughhousing brothers, they live in a comfortable house near the Hawaiian coast, where the kids have all become junior surfing stars under the tutelage of the old man, a former pro who still hits the waves with his wife despite a bum knee. She’s so good, and so pretty, that she’s even been tapped for a modeling gig.

But one morning—the very day Tom enters the hospital for surgery with an avuncular doctor (Craig T. Nelson)—Bethany goes out surfing with family friend Holt Blanchard (Kevin Sorbo) and his son Byron (Jeremy Sumpter). Suddenly the shark attacks and her left arm is severed. The Blanchards get her to the paramedics and the doctor saves her life, but the limb, of course, is gone.

The core of the movie is concerned with how Bethany deals with her loss. Bolstered by her faith—she goes off with a church group to assist victims of the 2004 tsunami in Thailand and learns that others are suffering far more than she is—she returns determined to surf again despite the physical difficulties. Though she has to watch her best friend take over the modeling duties and the prosthetic arm made for her turns out to be a bust, she overcomes all obstacles to enter a surfing tournament, and comes close to winning it against her constant rival Marina (Sonya Balmores). But even though she loses—she has an amazing run but the judges disqualify it as coming too late—she’s won a personal victory that that inspires others who have suffered similar injuries.

This is obviously a feel-good story about a tragedy that’s turned to a good purpose, and Robb makes an engaging stand-in for Hamilton. The sequence of the shark attack and its immediate aftermath, moreover, is well staged and generates real tension.

But the screenplay, adapted from the book Hamilton wrote with Sheryl Berk and Rick Bundschuh, follows every convention and cliché it can muster. The incessant horseplay of the Hamilton boys becomes a sitcom joke, and there’s a skate-boarder named Kaoki (Cody Gomes) who’s infatuated with Bethany and follows her around like a puppy, though absolutely nothing comes of it. Balmores’ bitchiness is hilariously broad; even Quaid suffers from director Sean McNamara’s apparent encouragement to flash his goofy smile way too often. And the use of footage of the real Hamilton during the closing credits has the usual effect of undermining the recreation we’ve just watched.

But the worst element of the picture is surely the part that involves Sarah, the youth organizer at the Hamilton’s congregation. She’s played with an intensity that verges on the manic by singer Carrie Underwood, who on the evidence here shouldn’t give up her day job. There’s certainly nothing wrong with pointing up the religious component of the Hamilton family’s life, and its importance in Bethany’s courageous attitude. But McNamara and his colleagues employ it in a ham-fisted way that makes it less, rather than more compelling.

It remains to note that the Hawaiian locations are lovely and cinematographer John R. Leonetti captures them nicely. The sequences of surfing competition are well done, too. But one wishes the Bethany Hamilton’s story had been told with greater subtlety and imagination. As it is, “Soul Surfer” comes across as a mediocre treatment of any amazing personal triumph, and comes out more than a little waterlogged.