The 27-year-old singer accidentally showed her bare behind to the crowd when her bikini bottoms came off after riding a water slide at Raging Waters in San Dimas, California, reported Ace Showbiz.
The 'California Girls' singer, luckily, had her back to the paparazzi when her swimsuit sagged.
"Let's be fair, I really think I deserve a season pass for that...
Oh, and some flip flops," she wrote on Twitter.
The ex-wife of Russell Brand went to the water park just one day after she was spotted leaving a house party in Los Feliz with her alleged boyfriend John Mayer.