What could be the cause(s) of water on the the floor on the passenger side.

is it water or anti freeze? could be heater core if its coolant or a/c evap drain plugged and the drip pan is overflowing

You might want to check your heater core.Does your heater work? does your window fog up at the defroster vent? do you smell coolant? These along with the wet floorboard on the passenger side are signs of a leaking heater core.