In a new Instagram photo, Malin Akerman shows off her post-baby bikini body while holding 3-month-old son Sebastian while going swimming. Credit: courtesy of Malin Akerman

Bikini-ready just three months after baby! Malin Akerman showed off her slim post-baby body while wearing a sexy string bikini in a new Instagram photo.

The 35-year-old Rock of Ages actress shared an intimate picture of herself holding 3-month-old son Sebastian while standing near a pool. "I got to go swimming with this beautiful boy . . . lucky me! Parenthood. Love," she captioned the shot.

In the photo, Akerman cuddles an au naturel Sebastian to her chest before going for a swim. The new mom, who stars in the upcoming sitcom, Trophy Wife, made her first post-baby red carpet debut on May 19 -- less than five weeks after Sebastian was born!

Though the Swedish-born beauty looked stunning in a low-cut black mini-dress at the event, she told Us Weekly that she was still getting back into shape. "You haven't seen the cellulite on my ass and my stomach. Oh I'm telling you!" she joked. "But it's nice to cover it up with some clothes."