When it rains hard I find that the water on the passenger floor is wet. I've had this problem before on a car and found that the cowl drain on the passenger side was clogged. The problem is that there is no obvious way to get to the passenger side cowl drain. There is a cover that can get me into the center of the cowl but there is a hose holder that blocks access to the two top screws of the cover and it appears that the holder is held in place by two bolts with the side with the nut being on the other side.

 

Also remember that water can come from the windshield or back glass and end up on the passenger floor.

 

Yeah comes thru 3rd brake light