A damaged heater core will cause coolant or water to leak onto the passenger floorboard.
Its pretty much under the floorboard of the passenger side. Start ripping the carpet up where the passenger puts their feet and you'll find it.
The condensor drain tube is clogged. Find the drain line and unclogg it.
Have the coolant system pressure tested, the pressure test will increase the coolant leak.
It's under the carpet at the front passenger floorboard. Pull up the carpet a little from the top and you'll see a small glass window directly on the floorboard in the middle which contains a flashing red light when the key is on accessory mode. Count the flashes to find the trouble code.
How To Find & Fix Coolant Leaks http://www.aa1car.com/library/coolant_leaks.htm
you have to find where the leak is first.
It means you have a leaky heater core. You may also find the front passenger floor wet with engine coolant.
If it is just water and not coolant, then more than likely the A/C drain line is plugged. Crawl under the car, passenger side, and find the drain line near the firewall and unclog it. If it is coolant then your heater core is leaking and needs replacing. Test the water and if it smells or taste sweet it is coolant.
Losing coolant in a vehicle is not a good thing. It is best to check all seals and all bends in tubing.
Are you sure it is not transmission fluid? Oil in the coolant would indicate a bad head gasket
IN THE WATER JACKET.
Water, not coolant? The only place plain water can be found on a car is when it condensates from the air conditioning, if the drain hose is plugged it will overflow into the passengers side floorboard. Get a piece of wire and find the tube under the car at the firewall and unplug it.