It's clearly been nothing but smooth sailing for Gisele Bündchen and Joaquim Valente since having their first baby ... check out photos of the two from their recent boat day in Florida -- they can't keep their hands off each other!

The hot couple hit the waters in Miami over the weekend ... and the vessel's engine wasn't the only thing producing some steam.

Take a look, Gisele -- who was stunning in a black one-piece -- planted a few kisses on her shirtless man ... as he navigated the ship.

The duo was joined by some friends for the excursion -- although there was no sign of their newborn.

As you know, Gisele gave birth to her and Valente's child in early February. She previously had two other kids, Vivian and Benjamin, stemming from her prior marriage to Tom Brady.

Speaking of TB12 ... doesn't seem there's bad blood over the expansion of the Gisele fam on his end -- he actually got a heads up from his former wife about the pregnancy before media outlets sunk their teeth into the news.

Still, it's gotta sting at least a little for Brady to cycle through these pics ... although nobody cries for Tom, he's doing just fine.