Water inside my rear pass door

[chrismoore701]

So we had a pretty long rain yesterday. Head to work today and I hear a lot of sloshing coming from the back. Get to work and open the rear passenger door of my 2009 Silverado quad cab. You can hear it sloshing around. Pulled the weather stripping off the bottom of the door and had about 3-5 gallons of water squirt out from the trim hole from inside the door. Any idea of what I can do to eliminate this issue?