Shawn Mendes and his girlfriend Bruna Marquezine tried to cool down at the beach … but with all the PDA they packed on … things got super hot!

Shawn and his gorgeous actress gal were recently snapped showing off their killer bods … as they were all over each other in Bruna’s native Brazil.

As you can see … they were all smiles — that is, when they were not locking lips as the waves rolled in.

This kinda thing is normal for the couple … the singer-songwriter and the Brazilian bombshell have been snapped before showing some serious lovin’ at a Brazilian beach.