Gisele Bündchen Rocks Bikini as She Flaunts Post-Baby Body

Gisele Bündchen is flaunting her post-baby bod in a bikini just one month after giving birth to her third child.

Check out the pics ... you'd never guess the supermodel was pregnant just weeks ago with her super fit physique. She looked at ease as she lounged in a gray scoop neck bikini top and white bottoms while aboard a yacht in Miami Beach with her beau and baby daddy, Joaquim Valente, on Sunday.

She caught some rays as she relaxed on the bow of the boat with brown shades and her dirty blonde hair flowing freely with the wind. Her 12-year-old daughter Vivian joined her at one point for some mommy-daughter time.

She and Joaquim seemed to be in full new baby bliss ... with the jiu-jitsu instructor sneaking up for a smooch.

The boat outing was a family affair ... with multiple people on board. Vivian at one point snapped a pic of Joaquim and his family.

It's unknown if there was a baby on board ... as Gisele and Joaquim's newborn was not photographed during the excursion.

We broke the story in February ... the couple of several years welcomed their first child together -- just a few months after their pregnancy was revealed.

Their new bundle of joy was also MIA during their Saturday yacht cruise -- which marked Gisele and Joaquim's first time being spotted since they became parents together. Vivian was seen getting her tan on as her mother -- rocking a cheetah-print one-piece and black sarong -- stood nearby.

Also missing during both outings was Gisele's firstborn, son Benjamin. As you know ... she shares both Ben and Vivian with her ex Tom Brady.