Charli XCXbrought Brat Summer to the water for Playboy … stripping down and posing topless while riding a barge down a famous waterway in the United Kingdom.

The singer-songwriter posed for the iconic magazine in a cover story published Wednesday … putting her body on display in a hotel room — black bra barely covering her chest — before taking the shoot on the road. Or, more accurately, the water.

On the boat, Charli strips the top off completely … though she tastefully covers her boobs with her hands while posing in front of notable London landmarks along the River Thames.

Charli didn’t just open up her shirt … she opened up her heart … discussing her marriage to George Daniel … and admitting she’s got the hots for people who have the toxic trait of being “a tiny bit avoidant.”