Why is my Eldorado filling up with water?

We have a 2002 Cadillac Eldorado that started filling up with water. There is literally inches of standing water on the floor, condensation on all the windows, and all the upholstery is soggy. I’ve vacuumed it out and left the doors open to try to aid in airing/drying it out, but when I go back in an hour the water has accumulated on the floor again.

My husband drilled a few holes in the floor to allow the water to drain out, and we removed the back seat to see if we could find where the water was coming from. The water accumulates in the seat compartment where the seat was removed, and though the holes in the floor help drain the water somewhat, it still collects there. Now there is mold/mildew starting to develop and I’ve used a bleach water solution to try to arrest that, but I’m really getting sick of dealing with this car.

He says we can’t sell it until we get another 8000 miles out of it, but we can’t drive it when it’s all wet like this, and he doesn’t want to put any more money into it—HELP!

Do u park outside? Or does it rain a lot in ur garage? Sunroof drains are not plugged? So, car is dry. No rain. Next day, u have 2 inches in backseat?