Katy Perry's Bikini Bottoms Lose A Fight With A Water Slide (PICS)

What do you get when you add a celebrity + a bikini + a raging rapid?

This is the answer...

Oooh, what barefaced cheek, Ms Katy Perry!

The poor lamb was left red-faced when her bikini bottoms lost a fight with a flume, exposing her naked derriere at Raging Waters in San Dimas, California.

The singer grappled to the edge and frantically tried to pull them up to save herself any embarrassment, but she was too slow for those pesky paps who got their cheeky shot.

But undeterred, Katy got back on for another go.

Atta gal.

The star is rumoured to be currently dating former Hollywood lothario John Mayer, after being seen on a string of dates.

> IN PICS: KATY'S STYLE EVOLUTION