Proving that she’s not one of these celebrities who has to be perfectly preened before she greets her public, Katy Perry went to the water park with her pals and totally let her hair down.

In fact her hair couldn’t have been any flatter because it was quite literally stuck to her head with water.

She went to Raging Waters in San Dimas with a group of friends for a day which looked to be full of large laughs.

One of these came at Katy’s expense after she’d surfed down a chute. The force of the water was obviously so strong though that as well as giving her a hairstyle reminiscent of Justin Bieber’s brushed-forward lesbian do, it yanked her bikini bottoms down too.

Yep, she flashed the watching crowds her naked tush.

She didn’t seem to mind though and burst into laughter as a mate helped her up.

Basically loads of people now have Katy’s moon as the screensaver on their phone.