The supermodel and her jiu-jitsu trainer boyfriend had Benjamin and Vivian Brady in tow Sunday as they went paddleboarding for a second straight day in Miami ... all but confirming they are still together and going strong ... despite some rumblings they were dunzo.

On the contrary, GB and JV look very much so like a couple -- and here ... they looked like your run-of-the-mill blended brood ... with Tom and Gisele's kids tagging along.

Gisele and Vivian shared a board between the two of them ... while Joaquim looked to be giving Ben some tips as he backed up the retired QB in the dad department.

Tom was nowhere to be found during the family outing in Florida ... but that's because he was in St. Louis, MO for his TV analyst debut in the FOX broadcast booth for the UFL championship game.

It was a big SUP weekend for Gisele and Joaquim ... they also busted out the boards on Saturday, sending a strong message of unity -- and again, proving they're still banging.

Credit where credit's due ... Joaquim's looking pretty fit too.

The camera-friendly outing come amid rumors of trouble in paradise ... there were reports Gisele and Joaquim split as a result of stress in their relationship following Tom's Netflix roast.

Remember ... Gisele was pissed over a lot of the divorce jokes and Tom was clowned for being replaced by Joaquim.

But, based on what we're seeing here, GB and JV are dispelling all the breakup whispers. As for Tom -- he was busy obviously ... but it's good to know Joaquim can fill in at a moment's notice.