Leonardo DiCaprio, Vittoria Ceretti Take a Dip After St. Barts Yacht Party

Leonardo DiCaprio is still seriously smitten with girlfriend Vittoria Ceretti ... staying close to the Italian model's side during a beach outing in St. Barts.

Check it out ... the couple, who has been hot and heavy since linking up last year, looked as happy as ever while enjoying some fun in the sun in the Caribbean. Vittoria, who donned a little black bikini and white baseball cap for the beach day, was spotted smiling and laughing with friends while splashing around in the crystal blue water.

It didn't take long for Leo to follow suit ... as he trudged down the beach in a pair of cobalt blue swim trunks and joined his lady in the water. Not only did the Oscar winner take in the scenic sights, but he also got an eyeful of VC's backside -- which was on ample display in her high-rise bikini bottoms.

However, it wasn't just Vittoria bringing a smile to Leo's face on vacay ... he joined in on an action-packed game of beach pickleball.

Still, there's no denying Vittoria is Leo's favorite travel companion these days ... the pair was recently spotted grinding up on one another in matching all-black ensembles while partying on a yacht.

The duo looked totally in love as they held each other close on their tropical getaway.