Zac Efron is having difficulties training to be a lifeguard for the upcoming movie adaptation of the Baywatch TV series, according to the show's star David Chokachi.

The High School Musical actor began shooting the film version of the 1990s show alongside Dwayne "The Rock" Johnson, who is playing David Hasselhoff's character Mitch Buchannon, earlier in February.

Efron is playing lifeguard Matt Brody - a part originated by David Charvet - but is struggling to get to grips with the ocean, according to Chokachi, who played Cody Madison in the TV series.

"Alexandra Paul, who is Stephanie on the show, her husband trains triathletes and I know he's training Zac Efron to be ocean competent. Nothing against Zac, but I heard he's got a little struggle going on with his affiliation with the ocean ... He's having a little trouble, let's put it that way," Chokachi told E! News.


But he defended Efron, admitting learning be a convincing lifeguard on camera is tough and it took him months of training to get it right.

"People think, 'Oh, we're gonna go swim in the ocean'. But it's different. If you're actually going to portray a lifeguard, there's a lot going on - how you enter the water, how you get to a victim ... You gotta be legit or you're gonna look like crap on TV ...

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"I'm sure he's struggling because I trained for like three months before we started filming with a real lifeguard, Mike Newman. He kicked my butt. It was hard. The water's freezing, you're running in in your shorts, and you're spending a lot of time in the water, and the waves, you kinda get used to it."

Dwayne posted a picture of him and Zac on set on Instagram on Tuesday and wrote, "#BAYWATCH Day 1. My character 'Mitch Buchannon' just gave @zacefron's character 'Matt Brody' the all important beach speech about what it means to have manly 'Alpha balls'... World get ready to have some fun, 'cause the beach will never be the same again."

Pamela Anderson, who became the break-out star of the TV series, told Entertainment Tonight Canada that she turned down a role in the Baywatch movie because she didn't like the character's storyline.

But she revealed she is still considering a cameo.

"I haven't turned it down completely yet, but I have turned down what they offered me," she said. "We'll see what happens."

Hasselhoff is also in talks for a cameo appearance.