Jessica Biel Rocks Tiny Bikini Bottoms to Play Paddleball With Shirtless Justin Timberlake

You know what they say about the couple that plays together!

Jessica Biel and Justin Timberlake put that theory to the test during a beach getaway to Puerto Rico last week. The pair hung out at the water's edge July 15, where they played a game of paddleball.

Biel, 30, sported a skintight, white wetsuit top and showed off her toned derriere in tiny black bathing suit bottoms as she hit the ball back and forth with her shirtless fiancee, 31, who rocked boardshorts.

PHOTOS: Justin Timberlake and Jessica Biel through the years

How does the "Total Recall" actress keep her body beach-ready?

"For me, getting enough sleep, drinking lots of water, having a healthy diet and staying away from alcohol are musts," she told ELLE last June. "It's so boring, I know, but doing those things really helps."

When it comes to her workouts, she's also a big believer in mixing up her routine by alternating between boxing, martial arts and yoga. "Yoga is a constant for me because it keeps my muscles long and flexible," she explained to the mag. And when the weather heats up? Biel says she makes time to hang out in the sun, "playing volleyball and jogging with my dog, Tina."

PHOTOS: More celebs who got engaged this past winter

Timberlake and Biel have dated off and on for the last five years; the pop star proposed to Biel over the holidays with a $130,000 diamond sparkler.

Sources tell Us Weekly the stars are in the midst of planning their summer nuptials.

"It will be a big wedding," one insider shared. "They have lots of people they want to invite!"

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