You gotta see the pics — Cruz turned his Amalfi Coast, Italy yacht trip into an R-rated peep show Wednesday … rocking a teeny blue Speedo, bulge front and center for GF Jackie Apostel, who wasn’t shy about yanking him even closer with a handful of Beckham’s bum for good measure.

Jackie was literally gazing up at Cruz aboard the Bulge Voyage, inching closer and closer — basically setting the stage for the racy moment everyone thought was about to go down.

But turns out, it was more giggles than grinding — Cruz cracked up and his 29-year-old GF threw her head back laughing too … so looks like they’ll be saving the real action for the bedroom.

But can’t really blame ’em for mixing it up — after weeks of sunbathing, tanning, and living the sea life, Cruz and Jackie clearly just felt like adding a little extra spice to the yacht menu.

Let’s just say … Amalfi isn’t the only thing leaving them breathless.