Katy Perry Loses Her Bikini Bottom During Outing at California Water Park (PHOTOS)

I'm going to be honest here: Katy Perry's got a fabulously beautiful bottom.

And it's in full view here, amazingly. She's practically nude!

See: "Katy Perry Bikini Bottom Slips While Boogie Boarding at Raging Waters in San Dimas."

You gotta love that babe. Smokin'!

Don't miss those photos!