Shawn Mendes Packs on PDA with Actress Bruna Marquezine in Ocean

There's nothing holding Shawn Mendes back from putting his hands all over his new lady ... because he was spotted getting close to his girl Bruna Marquezine!

The singer-songwriter hooked up with the Brazilian bombshell off the coast of Alagoas -- a state in the South American country ... eyes closed, lips tightly intertwined while they waded in the crystal clear water.

It ain't easy to bring saltwater to a boil ... but, these two certainly gave it their best shot with some passionate PDA.

Shawn and Bruna's afternoon delight came just a couple weeks after we saw them leaving an airport in Brazil together ... before they grabbed dinner at a Rio de Janeiro restaurant.

Bruna wore a tiny black dress to the occasion which left little to the imagination ... while Shawn attempted to keep a low-profile in a black shirt and jeans.

The two have been traveling together a ton as of late ... and, it looks like their relationship didn't die with the stroke of midnight on New Year's Eve.