Hey! Tricky, but if you're not comfortable with the 'choreography' descriptions, maybe try small things and subtext. AR-1 makes a kissing noise, AR-2 scopes out Prot-1's wet body and makes a comment while Prot-2 walks in, double-takes, and goes about his/her business until another more graphic comment is made by AR-3 and then whichever AR is most dominant shoves Prot-1 and gropes him. Build the tension through dialogue before the grope and block an aggressive movement that requires intervention. Less can be more effective than full-on graphic.
Good luck, sounds interesting!
Small things and subtext looks interesting, thanks. But I forgot to mention the two important details. First, the Prot-1 is not naked: POW camp located in the desert, on a desert planet, so the Sand Is Water in the shower room. Second, Prot-2 is a subject of Obfuscating Insanity, being actually perfectly sane Double Reverse Quadruple Agent who knows (or being more correct, guessing) something important about Prot-1 and intends to cover him.

Hello! One of the first scenes in my current work contains a scene where one of the protagonist is being subjected to an attempted rape. Context — shower room in a desert POW camp, him alone vs three attackers, former Army of Thieves and Whores plus Doom Troops. Why this scene is needed — the first protagonist, who is a subject to rape, got help from the second protagonist, so this scene is doubled as Establishing Character Moment for him. I tried to write it, but first draft looks ABSOLUTELY silly, so I'm asking for help from more experienced writers.