Complete car diagram

I have a very mysterious water issue. The back passenger side floor carpeting is wet. There are no apparent leaks. I shop vac the water and in a few days it's soppy wet again. I'm wondering if the moisture is coming from underneath. I want to see a diagram to try to figure out where the water is coming from. I've only had the car for a month and wondering if the previous owner had spilled a LARGE amount of water there maybe vacuumed it up and it's soaked down so much that it keeps surfacing or what. We are totally baffled by this.

remove the rear door panels and check that the plastic is properly installed and that the drain holes are open