95 buick roadmaster is leaking water in the floorboard

If the water is clear and has no antifreeze smell, then its a blocked condensation drain from the AC. Most likely. You should be able to clean it out quite easy. It will be in front of the passenger side feet area. You may be able to see it from under the hood, or you may have to go from under the car.
Look for a crinkly tube sticking down or it may be a 2- 3 inch downturned L shape tube on the firewall. A pipe cleaner from any tobacco shop will do the job. Just poke it through to clean out. Watch out for water in the eye.

If the water is greenish or orangeish, and feels sticky then you have a heater core leak and will need to replace the heater core.