I have water leaking in under the front driver side seat.

Most likely it's the sunroof...youtube how to fix a leaking sunroof

Get your heater core checked. May be leaking.

under the wiper arms is a big cover ,lift the bonnet and look at the back behind the firewall and where the wiper motor is and either side of the vehicle is a well and in the bottom is a drain hole ,look and find then make sure these holes are clear so any water can run out

A leaking heater core will allow water to run out of the case under the dash and pool under the carpet.

sounds like your ac drain is plugged up and condensate from evaporator core is leaking inside

It could still be a leaking windshield and running under the carpet.
Or it could be a door gasket or one of the roof drains is plugged up.
You may need a body shop to check it out.

I had the same problem with a 1994 Taurus. Within the front fender was 10 years of pine needles and leaves blocking the drain backing the water up in and over the fire wall and into the front passenger seat floor.
I took a LONG pair of needle nose pliers threw the passenger side door, and was able to remove enough debree. After pulling out out about 5 fist full's of yuck, 1 gallon a water that was stuck some where poured out flushing out the drain. I did the same on the drivers side. After that I had no problems with floods. I hope this helps. If not check your back door weather stripping if you have one. I have heard water leaking behind the passengers seatbelt and onto the floor from under the seat. Got to love Florida's rain season(s)

Check all the seals around your windows and doors. Leaks could seep in through there drips at a time and fill the seats. also check the seals around your front windsheild.

We had same--water on driver side rear floor (soaked!). Driver side front floor seemed dry until feeling UNDER rug, was slightly damp. We found the location of TWO leaks causing this.

Leak #1 was through the parking brake line/cable seal; Recaulked with silicone. Removed plastic trim on floor between floor and door to reveal metal channel filled with water.

Leak #2 was where the door meets the car, near the hinge. It was the accordian-looking tube housing the wiring for the door. The big, rubber, circular plug connecting it to the main part of the car had come loose and water ran down through that, into the SAME metal channel filled with water from leak #1; will seal with silicone.

Note: We found that the channel filled extensively near the front door, BUT the carpet edge from the floor near the rear seat was dipping into it, wicking it up to the rear floor. Also, upon acceleration, the water in the channel gushed toward the back, thus soaking the rear carpet.

These leaks were found by removing all plastic trim (covering edges of carpet by doors), then one of us pouring water into specific areas of the exterior of the vehicle, and the other one watching closely with a flashlight for any signs of dripping.

I have the same exact problem.....1999 Galant! The water is in the center of the floor board and also under the seat to the back floor board!!