my car had a leak in the left taillight, and the rear bench was SOAKED! Anyone who sat back there got their pants wet 2k.
The water ran down along the left side of the car, behind the inner panels.
So not only did I have a small pool in the rear trunk on a rainy day, I also had the biggest sponge ever as a rear bench.
Took off the lights, and used some sealing compound along the gasket, and the problem was gone.