Leighton Meester Flashes Butt in Skimpy Bikini

Leighton Meester and Aaron Himelstein in Rio de Janeiro, Brazil April 14, 2012. Credit: GADE/AKM-GSI

This vacation keeps getting better!

Leighton Meester and her new artist boyfriend, Aaron Himelstein, took their PDA parade to the beach while on vacation in Rio de Janerio on Saturday.

Dating for five months, the couple looked comfortable and affectionate with one another during their Brazilian getaway.

And the Gossip Girl star wasn't shy about showing off her bikini bod in colorful halter top and barely-there bikini bottoms.

Meester, 26, splashed around with her shirtless man in the sea while having fun conquering the big waves.

"He's been around for a while. She's been with him since at least November," a source tells Us Weekly. "He dotes on her. She definitely likes that in guys."

Tell Us: Do you think Meester and Himelstein make a cute couple?