Shawn Mendes and Camila Cabello Make Out on Miami Beach

Shawn Mendes and rumored GF Camila Cabello are definitely getting closer and closer, as everyone on South Beach is seeing ... thanks to a splashy make out sesh.

Shawn and Camila brought what certainly looks like a budding romance to Miami ... snuggling and playing Monday afternoon in the sparkling blue waters. Good ol' fashioned PDA done right!

Camila's looking AMAZING in a cute white one-piece, showing off her flawless figure from all angles ... and Shawn's flaunting his six-pack. It's really no wonder they're all over each other.

Shawn and Camila have been pretty coy about their relationship status so far ... but they've been smooching and cuddling all over the country this summer ... Los Angeles, San Francisco and now Miami. Yes, their love is looking very bicoastal.

We only say "looking," because doubters suspect the romance is really about promoting their "Senorita" duet. However, that was released well over a month ago, so maybe it's time to consider it could be real. Who knows? They won't say.