Selena Gomez Cara D. Floats Her Boat for Bday Bash

7/23/2014 12:02 AM PDT BY TMZ STAFF

Selena Gomez celebrated her 22nd birthday in St. Tropez with smoking hot model Cara Delevingne -- who famously celebrated  … other stuff with Michelle Rodriguez.

Now Cara's got Selena's back. We're undecided about her front … for now.  tmz-on-tv-3