Water In driver side floorboard!!
 

Hello, I have a problem. I just got my car back from letting a good friend of mine use it when he was considering buying it off of me. As soon as i sat in the seat I noticed a smell... like wet swimming trunks, I assumed he went swimming and like an idiot left his swimming trunks in my car overnight and it caused a smell. I woke up the next morning after letting the car air out over night to notice that the smell was still there so i searched my whole car to find that underneath the driverside floor mat there was a wet puddle of water on my floorboard!!! there are no leaks in the firewall or anything so I assume its from the weather stripping on the roof, or an A/C leak? help please