You heater core has most likely kicked the bucket. It is anti-freeze leaking in your car. You should get that fixed ASAP (obviously!).
Heater core leaking?
The heater is leaking coolant.
Water is leaking on passenger side floor board when heat is on
Heater core has failed.
The ac drain is plugged. The drain hose is on the firewall on the lower passenger side. ...that, or your heater core is leaking.
Antifreeze leaking from the heater core.
Check for a sickly sweet smell. The heater core is probably leaking coolant into the floor. The core is not repairable but can be replaced.
Passenger side floor? Could be leaking heater core
you could have a heater core leaking or your windshield is leaking and the water is running down behind the dash and onto the floor.
There is a drain on the outside firewall that is clogged.
Heater core is leaking
heater core may be leaking or hole in floor