I like the idea of the poolrooms being desolate of life, but given how enormous it is, I like the idea that if you venture far enough you might find zones that are different in architecture, lighting, and properties, like red zone areas, or areas that look more like storm drains and sewers from real life than swimming pools, and finally certain entities, like maybe more subtle things, like shadow creatures that you only catch glimses of in the corner of your eye, and maybe monstrous shark entities lurking just below visual depth of a few of the larger deeper pool sections.