They meet a totally naked man (in which only his backside/buttocks is shown).

There is a naked female creature. Full nudity but she is wearing a cover costume for movie purposes that makes this scene of her nudity not clear.

Though the Creatures are naked, they are wearing a cover movie-costume (like the blue woman that plays in X-men) that makes their butts not humanly clear, genitals aren't seen and it's night time.

Man watches another man with binoculars who is naked but the nude man is far off in a distance.

Female nipples are seen more clearly through movie costume. She begins to run and you can see her butt outline through the movie bluish costume.

While the younger man is on the lower floor, he hears noises upstairs, implying sex.

killing of the creatures would be disturbing for some viewers