Here's Camille Kostek -- ex-New England Patriots cheerleader and possible Rob Gronkowski GF -- struttin' around the beach in a butt baring bikini.

Kostek is currently vying for a coveted spot in the upcoming Sports Illustrated Swimsuit Edition and seems to be a front-runner ... at least, judging by the positive response on social media.

It's clear Camille's feeling herself these days -- check out the bathroom video she posted.

Swag.