Standing on a surfboard is like trying to stand on soap," says Kate Bosworth. "You're going to fall." Which is why landing the lead role in the hang-10 flick Blue Crush posed such a challenge for the neophyte. "She was out taking surf lessons before she even got the callback," says director John Stock well. And after too. For two months last year, in L.A. and in Hawaii, where Crush was filmed, Bosworth, 19, spent seven hours a day in training: running, swimming, lifting weights and surfing—or trying to. "You just have to keep an 'I-just-have-to-get-back-on' mentality.' And that's what I did."

In between dancing to Counting Crows CDs and downing Ben & Jerry's Half-Baked ice cream with costars Sanoe Lake, 23, and Michelle Rodriguez, 24. "We all clicked," says Lake, a veteran surfer who offered Bosworth "little hints" so she wouldn't "look like a dork." Fortunately, Bosworth—a champion equestrian from Darien, Conn., who first acted in 1998's The Horse Whisperer and now lives alone in L.A. —has other things on her mind now. Like calling back east to her dad, Hal, 53, a Talbots executive, and her mom, Patti, 53, a homemaker, to check up on her three cats. Or throwing a strike with pals at a local bowling alley. Oh, and maybe meeting a guy—but dabblers beware. "I'm a relationship girl," she says. "You can't run from love."