I saw a video of a kid who rigged up a slide out frame for a curtain, no big deal I thought until I saw the "floor". Yes he put a floor in his, and used the foam floor panels like what people put in kids play rooms. He drilled a bunch of holes in the foam so it could drain, and he had a hose attachment that he could hook up a hose to drain the water away. I plan on the 3 leg fold out style.
I plan on doing something like he did for the floor, but I am going to have a boat bilge pump or maybe a small pond pump to pump it to a gray water tank if I want to. ( or 50 feet away to the woods if allowed ). The pump will just sit in the corner and I will cut the foam floor out to fit the pump. Most bilge pumps draw about 1.5 ah, so running it for 10 to 15 mins is no big deal. One reason for using the bilge pump is they are designed to handle small items in the water and not jam up.
https://www.youtube.com/watch?v=3WxVxPxQKA8