text: Supermodel Maggie Rizer only gave birth to her daughter Cecilia Kathryn nine weeks ago, but the mother-of-three is already back to her trim and toned self. The 37-year-old fashion veteran sported a tiny string bikini as she posed with her two-year-old son Quinnlann Clancy for a sweet snapshot, which she shared Monday on her Instagram account. 'Boogie boarding with my baby,' she captioned the image. And online commenters couldn't help but note how fit Maggie looks only a few months after she and her husband Alex Mehran welcomed their first daughter into the world. Beach body: Supermodel Maggie Rizer donned a string bikini while playing with her two-year-old son Quinnlyn Clancy on the beach - just nine weeks after she gave birth to her daughter Cecilia Kathryn . Bundle of joy: The 37-year-old shared this precious baby photo to announce the birth of her third child and first daughter on February 9 . 'That body is right back!' one Instagram user posted, while another added: 'I. Just. Don't. Understand. [sic]' Maggie thanked her commenters for being 'very kind' before noting that she takes great care over which images she chooses to share on her account, saying: ‘I post carefully!’ But one fan insisted on giving the model credit for getting her amazing body back into such great shape so quickly, writing: '@maggierizer there's not enough careful in the world to make me look like this even though I have ONE kid and she's almost two. You are killing it! [sic]' And Maggie has been working hard. Two weeks before her family vacation she shared a picture of herself on a Pilates reformer. 'Can't be a slacker forever I guess,' she captioned the photo of herself working up a sweat. Happy family: Maggie posed next to her husband Alex Mehran to celebrate their newborn's 'first trip to the beach' Date night: Maggie and Alex were pictured enjoying a romantic dinner later that night . Maggie and Alex, who also have a three-year-old son named Zander, are spending time with their family, including their newborn at an unidentified tropical destination. Another Instagram snapshot, which was also posted yesterday, shows Maggie sporting patterned shorts and a pink tank as she poses next to Alex, who is holding their baby girl. 'Cecilia's first trip to the beach!' she wrote. Later that night, Maggie shared a picture of her and her husband enjoying wine and a glass of something bubbly during a romantic 'island' dinner. Maggie, who announced Cecilia's arrival into the world with a precious Instagram photo on February 9, continues to chronicle her children's adventures and their precious family moments on the social media site. Getting toned: Two weeks before her beach vacation, Maggie shared this photo of herself working out on a Pilates reformer . Pretty in pink: Maggie and Cecilia donned matching pastel outfits for Easter . All bump: Maggie showed off her growing belly with a selfie she took in January . Maggie rarely models but remains in demand, despite having moved to San Francisco for her husband's work. She was last seen on the catwalk in September 2014 at Michael Kors' New York Fashion Week show. Though her pregnancy was not public knowledge at the time, she would have been four months' pregnant - a point at which most expectant women start to show a small bump. Maggie, who originally hails from New York State, was one of the world's most popular models in the late Nineties and early 2000s. She stopped modeling in 2004 after it emerged that her stepfather, John Breen, who had been handling her finances, gambled away her entire fortune. Her professional earnings alone were estimated to be over $7million, though she also lost inheritance left by her biological father, Kevin Rizer, after his death from AIDS when she was 14. Since the loss of her father - her parents divorced when she was a baby when Kevin announced that he was gay - the model has been a staunch AIDS awareness activist.
target: The 37-year-old welcomed her first daughter Cecilia Kathryn into the world on February 9 .
  Maggie and her husband Alex Mehran are also parents to two sons, three-year-old Zander and two-year-old Quinnlann Clancy .
  The parents are enjoying a beach vacation with their three children .