This is one part of Katy Perry that she never, ever wanted us to see.

Being the 'California Gurl' that she is, K.P. decided to hit the wave pool and try her hand at boogie boarding, aka the poor (and uncoordinated) man's surfing. Unfortunately, the manmade rapids at Raging Waters in San Dimas, Calif. were too much for her to handle, and the 'Last Friday Night' hottie wiped out.

To make an embarrassing situation even more blush-worthy, the ride ripped off her bikini bottoms along with her sense of pride. Paps were of course standing by with cameras, and they probably almost dropped dead at the sight of the songstress' naked butt. *Ka-ching!*

If you want a glimpse of Perry's patootie, click here to check out the NSFW photo of her bare backside.