Water on floorboard by gallons

Okay, a few things, These are known for plugged sunroof drains. There is a rubber line that runs from the sunroof down through the drivers side pillar and out the bottom of the car. These get plugged over time. There are a few ways to clean them. The easiest is to find the drain outlet under the drivers side of the car, then open the ducksbill at the bottom and see if the drain is plugged there. If not then you can use compressed air to gently blow the dirt/crud out of the drain. But this method can also make the drain line fail if you are not real careful. The better way is to remove the trim around the door and front pillar, remove the drain tube from the sunroof and clean it out using air and water.

The other item is that the windshield seal goes bad and they leak around the glass.

Both of these are common on these cars.

Another one is the AC drain. If the water started when you started using the air conditioning and gets worse when you use it the drain from the HVAC unit is plugged. It exits on the passenger side of the firewall down at the bottom, there will be a 90 degree elbow that you can see and use a wire to see if it is clear. This one will usually be accompanied by a sloshing sound as the water in the HVAC case moves when you turn.