The 27-year-old goddess and famous 41-year-old DJ are kicking it in the picturesque town of Tulum ... where they had trouble keeping their hands off each other. They got super cozy and very wet ... taking a dip in the Caribbean waters while getting super handsy.

It appears this is their coming out party as a couple. Chantel posted several stories on her Instagram showing her relaxing with Diplo, who strokes Chantel's hair and calls her "baby" when she pans the camera his way as they laid back on a hammock.

And, Diplo's already embracing the "Instagram boyfriend" lifestyle ... 'cause Chantel just posted a series of pictures of her sexy self in a yellow bikini, but the last pic shows Diplo's the one putting in work and snapping away. Atta boy.

Gotta give Chantel credit for bagging herself yet another baller. She's previously been linked to Machine Gun Kelly, NFL star DeSean Jackson, NBA stars Jordan Clarkson and Kyrie Irving as well as Justin Bieber and The Weeknd.