Dwayne Johnson is more than a little envious of Zac Efron's "nice tits".

Zac Efron in 'Dirty Grandpa'

Zac Efron in 'Dirty Grandpa'

The actor, also known as 'The Rock', will be starring alongside Zac in the upcoming movie remake of hit television show 'Baywatch', and was quick to compliment his co-star on his physique when Zac shared a photo from his new film 'Dirty Grandpa' on Instagram on Wednesday (30.12.15).

Zac wrote alongside the snap: "It's been a life long dream of mine to work with [Robert] De Niro. Lo and behold, I spend most of the movie naked or in women's clothing. And you know what...it was TOTALLY WORTH IT. I can't wait for you to see @dirtygrandpa - it's hilarious! Save the date for a wild (and really weird) ride on JAN 22 #dirtygrandpa."

The picture shows Zac wearing an orange crop top which features the slogan "Stop staring at my tits".

And Dwayne was quick to comment on the picture, writing: "Nice tits brother. See you soon."

It was announced earlier this year that Dwayne and Zac would be starring in the 'Baywatch' film, following the former success of the show that launched the careers of David Hasselhoff and Pamela Anderson.

The admiration between the actors definitely seems to be mutual, with Zac admitting he was thrilled to be given the chance to act alongside 'The Rock' himself.

He told chat show host James Corden earlier this year: "I'm so excited, he's like the coolest dude in the world. He's like a real life Superman."