Memorial Day weekend marks the unofficial start of Summer 2010. And just like the rest of us, sun-worshipping celebrities will soon begin showing off their bronzed bodies on beaches all over the Northern Hemisphere.

While we wait for the mercury to rise, we're turning up the heat with these 17 pics of musicians caught off-guard while frolicking in the sand and surf. Which stars have the hottest beach bodies (and which ones need to spend a little more time with their personal trainers)? Ogle away at paparazzi pics of Beyonce, Justin Bieber, Ke$ha, Britney Spears, Katy Perry and more, then share your thoughts in the comments below.