my passenger side floor board is full of water(just water) what could it be?

Thank you for answering so quickly Williamss....I called the nissan dealership and they said it may be that or the sunroof drainage?? How can I check this myself and not have to pay them to fix it?? Thank you so much for your help

after a drive with your ac on leave car running and look underneath passenger side around the firewall area to see if water is dripping that should be your ac drain tube. i noticed you said after a rain it is worse so probably is a rain leak the vents out in front of your winshield where the windshield wipers are located also have drains check and make sure they are not stopped up with debris like leaves and stuff this is also a good source for leaks