'Baywatch' Star Alexandra Daddario Reveals She Gained Weight Ahead of Bikini-Clad Role

Paramount Pictures

Alexandra Daddario had a surprising goal when training for her role as Zac Efron's love interest, lifeguard Summer Quinn, in theupcomingBaywatch movie.

"Really, I've never done anything where I've thought about my body as much. You are literally in a bikini the entire day," she tells the June issue of Women's Health. "I even wore a swimsuit when I auditioned with Zac."

In preparation for the movie, Daddario reached out to the man responsible for Efron's abs, trainer Patrick Murphy, and was ready to gain some weight in the form of muscle mass -- or as Murphy calls it, "visual lines of definition."

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While the hour-long workouts were quite strenuous, Daddario says she still trains with Murphy because she's so pleased with the results. "For the first time in my life, I have real abs!" she exclaims.

Daddario elaborated to ET about what it was like shooting scenes while wearing minimal clothing, and noted that body confidence is crucial when shooting a film like this. "I turned 31 recently, and through my 20s I learned that as a woman, being confident with how you look and how you feel is the most important thing," she said. "I think no matter what, there's always something that you're going to criticize about yourself. Confidence is attractive, and confidence is sexy."

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The actress also revealed what it's like to touch Efron's "incredible" abs. "He's, like, not human," she insisted. "He's, like, something Michelangelo carved."

Baywatch hits theaters on May 25.

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