The driver side deep well formed where the quarter panel meets the trunk, inside the trunk, filled with water. There is an apparent drain hose that traverses that space as it heads to the outside that may be the culprit, but I would like to know where that drain hose comes from. What does it drain?
Do you have a sunroof?
I don’t think there is a drain hose that is the problem . I would suspect the rear window seals or a leak near the tail light. You did not say if this is rain water or how long it takes to have enough water to be noticed . Also you might consider drilling a drain hole unless this 22 year old vehicle is in really good condition. Dry the area out and then use a water hose and see if you can find where the water is getting in.
Thank you for the prompt reply.
Timing is an unknown, but there was no hint of rust anywhere. The trunk mat was damp near the fender/trunk junction, but there was so much rain water in the space (maybe 4-5 inches?) that it could have sloshed up enough to dampen the mat. Also, because a Samaritan had assisted the owner in exploring how to open the fuel cover when its spring had broken, the “felt” lining above the leak site had been removed and replaced, placing tension on the drain hose and keeping it from being secure within the grommet. The drain hose was not fully inserted through its grommet (that led to the outside), so I’m thinking the water may have been dumping into the site from the hose rather than exiting to the outside. The hose was not snug at all within the grommet, until we beefed up the hose diameter by taping around the hose. We’ll test the window seal (thank you!) and tail light for sure.
Thanks so much for your great input!!