Cowl vent problems

I am having a problem with water flooding the floor board of the passenger side. After searching around I believe the vents under the windshield are the problem. Does anyone know how to get to the passenger side vents. My dad had called them "cowl vents" I believe. If anyone also has any other ideas about what this problem is. The passenger carpet is the only spot that is wet and I know the water is coming from behind the dash.

fresh water, or coolant? does it have a smell? in most cases the water on the passenger side floor board is coming from a leaky heater core.

Look under the heater motor in the engine compartment. There is a vent/drain there that gets clogged, once that happens, water fills the heater box and leaks out into the passenger side floor.

Common areas for water leaks are door seal gaskets, blower motor-A/C line-heater hose gaskets, windshield seal/gasket, blocked A/C drain valve, the grommet for the AM/FM radio cable, improper application of body line sealer from the factory, and holes in the floorboards.

Have a helper sit inside and use a garden hose to spray around and locate the leak.

The cowl vent is the panel between the windshield and the hood that the windshield wipers pass through.

Look at this seam, on the passenger side, above the blower motor. We've had two leak here. The water tracks down the firewall, and wicks through the foam rubber around the motor, and hides under a floor mat, if you have one. I have fixed them with silicon caulk. Have someone shoot the garden hose onto the driver's side, and watch this area to see if the water weeps out there.

To respond to one question, it is rain water. I'm not a mechanic at all, I giving all your great answers to my dad, so this question seem dumb but how would we get to these vents and drains with as little chance to breaking something else. Oh and its a 1990 Jeep Cherokee limited (reconstructed)