Jennifer Garner and Ben Affleck (Photo : Reuters)

Many celeb mothers could take a lesson or two from Jennifer Garner who looks back in shape as she flaunts her sexy post baby body in a retro swimsuit. The 40-year-old actress was spotted on Puerto Rico beach enjoying a day with husband Ben Affleck and their three children,

Garner and the kids -- daughter Violet, 6, Seraphina, 3 and son Samuel, 4 months, came to Puerto Rico to join dad Affleck, who's on location filming Runner with Justin Timberlake, 31.

The beautiful family hit the beach early this week and Garner and Affleck showed off their impressive beach bods. Jennifer Garner is quite relaxed in the efforts to get back her pre-baby body. Instead of gushing to shed pregnancy pounds and wear bikinis, the mother of three looked like a normal mom. 

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The actress splashed around in the water with her daughters before grabbing her sundress cover-up to go for a walk with her baby boy.

Little Samuel was kept shielded from the sun with a large hat as he watched his siblings play.

When Affleck isn't spending quality time with his family on the beach, he's been hard at work on his new film. Runner is about a businessman who gets caught up in the world of offshore online gaming.

The couple toasted their seventh anniversary on June 29 and a source recently told Us Weekly that they are debating whether to have another child.

"Jen is happy with three now that she has a boy," the pal said. "Ben wants four."