I believe you have a clip on each side, way up high, under the gas/brake pedal. It should just be a plastic screw type clip. Not sure exactly how they attatch, but I wouldn't lose much sleep over it.
I dealt with about 3" of water in my floorboards last summer as a new jeep owner. (didn't even know they had drain plugs) I pulled the front cargo area carpet to let it dry out. The insulation that is glued to the bottom of the carpet was pretty much destroyed, so I pulled it off and just put the carpet back in. Fits kinda loose, but it's ok. While I had the carpet out, I sprayed some truck bed liner paint in the floor board pans to help withstand rust. It won't be the last time my floorboards get water in them.