Leonardo DiCaprio and Vittoria Ceretti are living it up before summer comes to an end … living the high life on the high seas with a little luxury yacht time!

The actor and his model GF were spotted off the coast of Spain near Ibiza Friday afternoon … stripping down to just their swimsuits and soaking up the summer sun.

Check out the pics … LD’s only got a pair of black shorts on while VC’s wearing just a tiny, animal-print bikini.

The duo paddled around in the water together for a while… with Ceretti’s backside cresting out of the water like a well-tanned island.

Later on in the day, Leo and Vittoria were spotted gettin’ real close while on the ship’s deck … a touching moment between the A-list couple.

DiCaprio and Ceretti have consistently hit the water over the last couple months … jumping off a yacht together near Saint Tropez just last month — so, they’re experts when it comes to a day of fun, surf and sun.