NFL star Solomon Thomas is used to the Jets, but he's enjoying a different form of transportation this week -- cruising around on a fancy yacht in St. Barts with his stunning girlfriend.

The 29-year-old New York defensive tackle was spotted making the most of his offseason near the Caribbean island alongside Kaylie Alyson ... with both ditching their clothes for some bathing suits.

They looked happy as ever as they had their fun in the sun -- which included lounging around on a raft and downing some drinks on the deck.

They also made sure to rinse off after hopping back on the boat ... and shared a kiss to cap off the romantic getaway.

Thomas -- who has made $38.3 million in his eight seasons in the league -- certainly has the funds to enjoy himself and bring some company along ... and after the Jets' disappointing season, it's nice to see him move past it with some R&R.

Thomas just completed his third season in the Big Apple -- prior to that, he played out west for the San Francisco 49ers and Las Vegas Raiders.

As for his relationship, they went public together last year ... and whatever they're doing to keep the love alive, it's working!!

Also shoutout to Solomon and Kaylie -- they definitely don't miss a workout.