Now that's a work out!

Amanda Seyfried posted the cutest picture via Instagram on Monday, showing her paddleboarding with her dog Finn.

"It was surprising, at first, that Finn was so eager to jump aboard," the "Mean Girls" star captioned the sweet snap.

"Now, I can't enjoy paddling without him. The same can be said of my life. #finnsite #drfoz."

In the candid shot, Seyfried's rocking a vintage bikini, while she paddles alongside her gorgeous Australian Shepherd. It definitely looks like she's got a fury water baby on her hands!

The 28-year-old told Ellen DeGeneres in May that she and boyfriend Justin Long enjoy paddleboarding together, too. The cute couple recently spent plenty of time out in the ocean while they were vacationing in Florida.

"What we did every night—my boyfriend, myself and our two friends—we would paddleboard to watch the sunset, and one night we were paddleboarding with some dolphins," she told Ellen.

"But I thought it was a shark and I was like, 'Wait, check the fin!' And then my boyfriend's like, 'I see the blow hole!'"

Clearly, Amanda, Justin and her pup Finn are big fans of the water -- and the "Mama Mia" star looks pretty amazing in a swimsuit.

What do you think about Amanda's cute pic? Tell toofab below and click "Launch Gallery" above to see even more celebrity beach bods!

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