What cause passengers side floor to be soaked
What cause floor in front passenger side to be wet
Leaking heater core
Heater core leaks, though possible in your case, usually wet both sides of the floor. I'd suspect the AC condensate drain under the right side of the dash to be clogged and unable to drain properly. Although, if you have a sunroof that you didn't mention, it could be a clogged or damaged drain tube.
Heater core bro.