Secret Diaries (1989)

A slim blonde with short messy hair is grinding on the bench in a sauna, face-to-face with a curvy brunette who’s got long dark curly hair. They’re making out hard, hands down each other’s pussies, fingering and licking in close-up — you see the wetness on their thighs. Behind a curtain, a muscular black guy with a beard is lying flat, watching, while a white dude with a mustache crouches low, peeking through the gap like he’s scared to be seen. The scene cuts to the women on a bed later, doing 69, then the blonde riding the black guy doggy style with deep thrusts. Camera stays tight during the oral, pulls back for the group stuff. The tension between voyeurism and direct sex plays out without dumb dialogue.