Gisele Bündchen's uncanny ability to morph back into perfect model shape just a month after having a baby has surfaced, and it isn't that deep.

In fact, Bündchen's secret weapon is the swimming pool where her favorite personal trainer teaches.

Fellow Brazilian, Leandro Carvalho, says that his supermodel client was a big fan of Brazilian Body Surf during her pregnancy, the Boston Herald reports. The water-based workouts, an aerobic blend of running and swimming combined with props such as fins, gloves and noodles, create an intense non-impact routine.

Carvalho, who is affiliated with Equinox gyms, can also take credit for the body of Victoria's Secret lingerie model Alessandra Ambrosio.

Carvahlo tells the paper that Bündchen was in "very, very" good shape throughout her pregnancy, in part due to the
"very athletic" workouts, which he says are great for muscle tone.

Maybe all that pool time is why Bündchen opted to give birth to son Benjamin Brady in the bathtub of the Boston apartment she shares hunky hubby/New England Patriots quarterback Tom Brady.

So, perhaps, it is no surprise that Gisele told People earlier this month that she did not gain much weight during her pregnancy and never really had to wear maternity clothes (rub it in!) and is now focusing on yoga and meditation, when she has time.

And while the beauty may have worked up a sweat during her water workouts, she didn't seem too worried about her date last month with photographer David Sims to shoot the new ad campaign for Brazilian sportswear company Colcci, with whom she has a contract.

Meanwhile, read how Brazilian beauty and "Shear Genius" host Camilla Alves approached getting back into shape right after having her second child with boyfriend Matthew McConaughey.