Newly engaged Dua Lipa and Callum Turner are so steamy together ... they needed the ocean to help cool them down!

The pop star and her fiancé were snapped pouring on the PDA while they were all loved up on a raft along Italy's Amalfi Coast ... all between plunges into the crystal-clear Mediterranean waters.

As for Dua ... we sure hope she used plenty of sunscreen, 'cause she was rockin' a skimpy polka dot bikini -- leaving lots of skin exposed and very little to the imagination.

The fire couple announced their engagement earlier this month ... spilling the exciting tea to British Vogue when Dua revealed her engagement ring was custom-made after Callum consulted her best friends and her sister.

The "One Kiss" singer said they’re just soaking in the engagement vibes for now -- no wedding planning yet. She’s focused on her tour, and Callum’s busy filming.

The exact timing of the engagement is a mystery, but the pair -- who started dating in Jan '24 -- had everyone talking by the end of the year after Dua was spotted rocking a ring on that finger.