Alessandra Ambrosio Caught Smooching Buck Palmer on Brazilian Beach

Alessandra Ambrosio and her boyfriend Buck Palmer stripped down for a hot day on the beach in South America … and an even hotter makeout sesh!

The Brazilian supermodel and her jewelry-designer beau enjoyed drinks — and each other — Tuesday at Boda Beach in Pernambuco, Brazil.

The two were snapped showing off their toned bods and getting in some heavy petting with onlookers nearby.

Alessandra wore a barely-there purple 2-piece bikini while Buck went with black swim trunks and a black cap.

Earlier this week, we saw the couple in similar embraces on the island of Fernando de Noronha … off the Atlantic coast.