This sounds like a typical ac condensation water spill inside the cabin. The ac evaporator generates a lot of water condensation when the AC is running, and the water is supposed to drain out through a drain pipe on the firewall in the engine bay. The drain pipe is at the bottom of the ac/heater core box assembly under the dash. The drain pipe is not easy to see, it's in the engine bay side about where the passenger's left heel would be if he pushed his foot straight forward.
The ac drain gets clogged with debris that finds it's way in through the fresh air vent. The water then collects in the box and eventually finds a seam to leak out of, onto the floor. By poking inside the drain pipe from under the car with a pipe brush or coat hanger, you can usually loosen up the clog.. and get showered with nasty stagnant water and dirt.
This job is best done with the vehicle on a lift. You could take the car to a repair shop like Pep Boys or something, and just ask them to clear the ac drain pipe. I don't think they would charge you for more than 30 minutes of labor.