Kate Upton Kate Upton

Even two-time Sports Illustrated Swimsuit Issue model Kate Upton feels uncomfortable in a bikini — at least sometimes.

In the model's film debut The Other Woman, Upton filmed a scene in which she runs down a beach in a teeny white bikini. But while you'd never guess from looking at the footage, Upton revealed she was "uncomfortable" shooting the scantily clad scene on Good Morning America Wednesday.

"It was funny because when we were filming that scene, you know, whenever you go to a beach, everyone's wearing bikinis, so it's just pretty normal. It's just part of life," Upton said. "But when you're filming a bikini scene, nobody's wearing a bikini. It's only you and 60 crew members."

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The large crew size is the difference between a movie set and swimsuit shoot, Upton explained, noting the latter only had about "five people," with whom she'd worked in the past.

But thankfully, Upton found support in her co-stars Leslie Mann and Cameron Diaz, who did everything in their power to put the model at ease. "These two saw that I was feeling a little uncomfortable — because anyone's uncomfortable when that many people are staring at you — but these two came and ran beside me offscreen," she said. "I've never had support like that before and it was just so amazing that I got that on my first film experience."

Watch the full interview below and get an inside look at The Other Woman here.

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