Water is leaking into my car, onto the floor, on the driver's side.
Water leaks can come from various sources: a clogged drain tube in the AC/Heater box can cause overflow through the heater vent, or faulty cowling can cause water ingress into the passenger compartment. With the battery disconnected, water needs to run over the windshield area while the driver’s floorboard is being inspected, to see where the water ingress is occurring. Once the source is found, then a repair can be formulated. You may want to enlist the help of a mechanic, such as one from YourMechanic, to diagnose the source of your fluid leak, and recommend the proper course of repair.