SI's model search hit the runway to cap off Miami Swim Week ... and it was good.

Rob Gronkowski's on-again, off-again GF, Camille Kostek, was one of 15 finalists rocking the new beachwear line ... which is for ladies of "all shapes and sizes."

There's a lot of All-Pro talent in the field -- but just 1 is getting picked to be in next year's swimsuit issue.

Bonus video: Some of the ladies got loose in a behind-the-scenes dance-off ... and it was kinda goofy. But still really hot.