Just dealt with this recently. In my driver's side case, floor was soaked like yours & driver front sunroof drain was plugged at the slit in rocker panel where it exits to ground. Cleared that with a paper clip & a bunch of dirty water poured out. Passenger floor was just damp, but was from the bottom corner of windshield slowly dripping inside, traveling down the outside of plastic trim in the footwell. Wasn’t able to get to it for a few weeks, so removed those floor plugs, and it prevented any more water from pooling up.
Resealed around the edges of my windshield gasket with NP1 polyurethane, and redid the sunroof to be safe. PO had sealed it, I assume due to misunderstanding the leak, but I don't care to open it. So far, so good. I live in a damn good testing ground for confirming leak fixes, hah. I don't recall wet floors when I bought it this summer, but noticed the above issues after I accidentally hit the sunroof button & broke part of their previous seal. Oops. I have since pulled the appropriate pins from the connector up there (shares same connector for overhead light switch) so that won't happen again.
Even though you can watch water come out the bottom, the slit in rocker panel is very small and only drains so fast, so can be overwhelmed, so the car wash issue makes sense. Easy drain hose mod for better flow & to prevent potential clogs is to remove the footwell side trim, pull the black drain tube out of the opening where there is some wiring, and run it through where you removed those plugs. Tube is just slightly smaller than the hole, and in my case sticks down maybe 1.5” on each side (don’t pull too hard when doing this). Driver side is kind of a pain to get out, and you also have the larger cluster of wires running over the drain hole, whereas passenger is easy. Footwell trim still fits over the hoses no problem. Thinking I may seal around the edge of the tube on floor, now that leaks are gone, although that area doesn't seem to get hit much from underneath.
Separately, had another leak-related issue I’m glad I found. Was noticing a little water at the rear passenger corner by grab handle & seatbelt, figured it was due to sunroof, but actually turned out to be the roof itself. Had a small patch of paint missing w/ surface rust that I'd been meaning to grind and repaint. When I did so, found a small pea-sized hole. Couple other small areas where paint surface was lightly cracking, and proceeded to find four more very small holes... so, I was getting very slow drips through roof landing above the headliner, running to that corner. I ground out any surface rust under the paint, used bondo & repainted. Not a single drip since I did all this, which makes me happy.
If it’s just your front floors, most likely it is/was only sunroof drains and/or windshield, not holes in the roof
but wouldn’t hurt to take a look up there. Lots of threads on the process, but pretty straightforward. Clean everything first, and don’t use silicone, only black polyurethane sealant like NP1 master seal or whatever you can find locally.
To find windshield leaks, carefully look around every edge of the gasket outside and inside. Not always easy to see. You can also pull on the edge… in my case, there were areas at the outside bottom passenger corner where it looked sealed, but easily pulled up with my fingernail... surprise, that's where the inside drip was. My windshield was replaced at some point, but they did use proper sealant in all the right places, I guess it just gave out in that area. I did the whole gasket just to be safe.
Drain hose:
Normal drain slit, in case you didn’t specifically locate it. It’s at the very front of side step (if you have them) behind wheel well.. a little in front of where the hose would come out
