What movie is this: Science fiction/ Horror film with group bath scene

I remember watching a movie a few years ago, probably from the late 90's, early 2000's, and I have no recollection of it's title. There was a group of people trapped in a house, who (i think) were slowing being killed by it's owners (i think). It was either science fiction, horror or both, and it was clearly done on a low budget/ very corny, and pretty bad. Anyways, there was a scene where a female owner is nude in a bath (hot tub? pool?) and she forces the group to get naked and go in there with her. I remember one of them was very hesitant to go in. Another sexual scene I remember was at the end where one of the men from the group has sex with the female owner (in a library maybe?). I hope that's enough information for someone to recognize what movie it is, thanks.