Rihanna wants to "borrow" Brooklyn Decker's boobs.

The singer and her co-star in Battleship are both envious of different parts of the other's bodies, and would love to swap for a day to see what it would be like.

"We are envious of each other's bodies. We decided that I'm going to borrow her butt for a day - and she's going to borrow my breasts," Brooklyn told US Weekly.