J Lo & Ben Affleck Pack on PDA on French Yacht Ride for Her Birthday

It's Jennifer Lopez's birthday -- and if you thought anything short of a nautical hot and heavy make-out sesh with her new/old flame, Ben Affleck, was on the table to celebrate ... you were wrong.

Bennifer 2.0 have fully come out as a public couple now ... and they did it on none other than her 52nd birthday -- for which they're celebrating on a yacht in what we've heard is in the South of France. Jen just threw up some steamy shots of herself in a bikini -- and if you think they're hot ... just wait 'til you get to the last slide. Big kiss for baby Ben!!!

This certainly feels like a full-blown "we're here" type of a moment. Until now, neither party had posted any BF/GF shots to their socials ... although they have certainly been photographed together of late acting like a rekindled couple.

We've seen them get affectionate with each other over these past few months -- even some kissing in public -- but nothing quite like this ... where they're fully embracing, for the whole world to see.

As far as where they're off to ... it's anyone's guess. But, word is they were docked right on the edge of the bay, facing the Mediterranean -- so it seems they're gonna be on the high seas of the French Riviera for a bit. Classic celeb getaway ... but means more in this context.

One last thing we'll note ... Jen definitely looks birthday/yacht ready fashion-wise, and Ben does too. He seems to have ditched his usual grey(ish) tee and cargo pants getup -- opting for a nice button-down. They both look great -- this may just be the photo of the year.