Rihanna and Brooklyn Decker Bond in Sydney

Singer Rihanna, 24, and model-turned-actress Brooklyn Decker, who turns 25 on Thursday, have become fast friends while promoting their upcoming big-budget film "Battleship." The ladies were even snapped sharing a hug while cruising Australia's famous Sydney Harbour on Monday. Decker was outfitted in a red dress, while RiRi, who's known for her sometimes wacky style, donned a denim button-down over denim shorts. Perhaps they've become close because they're the only two women in a cast of men, including "Friday Night Lights" hottie Taylor Kitsch, sexy Alexander Skarsgard from "True Blood," and the always dapper Liam Neeson from, well, just about everything.

A day earlier, former Sports Illustrated Swimsuit Issue model Brooklyn slipped back into her bikini to catch some rays at a pool sans her new gal pal. And just in case you were wondering, Mrs. Andy Roddick has not lost her fab beach bod since gracing the magazine's cover in 2010! She flaunted her physique in a barely-there black bandeau bikini.

Much to their dismay, fans will see a more covered-up Brooklyn and Rihanna when the action flick "Battleship" hits U.S. theaters on May 18.

More Celebrity Features on Yahoo!:

Follow omg! on Twitter