Need help with a movie title

I saw part of a movie awhile back, never saw the title or the actors/actresses names. I would guess it is from some time in the 90s or 2000s. It sort of had a lord of the flies vibe to it. There seemed to be a plot point where 2 teen guys had some sort of a relationship, one of them was for sure gay, and I think he was one of the 'leaders' of the group. The guy who he seemed to be involved with was taking a shower, and in the stall next to him a girl was taking a shower, and they were talking. The girl, thinking the guy was gay, joined him in his stall and asked him to wash her back. I guess he start to get 'excited', and she turns and looks down at his junk and teasingly says something like 'I thought you were gay, or was that just a ruse to woo me?' The guy and girl both had dark brown hair. Meanwhile, the 'leader' was watching the 2 of them on a monitor, and using a mouse, he clicked on the screen where their clothes were hanging, which made them disappear. Then he turns the power off, so the guy and girl run out of the shower to get their clothes, but they are gone. They find some sort of a florescent light/glow stick, and began wandering the building trying to figure out what is happening. There was another scene where the guy from the shower (I think), had his hands tied and was being marched nude down a beach, and was forced into a box in the ground, and I believe the group of teens had put some sort of bug/creature in the box before they closed it up. That is all I remember. I would really like to see the rest of this movie, so if anyone can help me with the title of this movie, I would be eternally grateful.