What is this Leak? And how do I fix the Body Damage?

[saurey]

[DIIRTY-30]

Looks like your collecting water under the battery tray if I'm not mistaken.. You would need to cut away at the area to clean metal and re-do the sheet metal.. Might want to take a look at your tail light seal, trunk seal. Also the area where the run off water from the roof passes out through the rear bumper. Should be a tube that comes out the flap, sometimes this can get clogged or punctured. Hope this helps!

[monty23psk]

Looks like a late model e30 which means battery might be in the trunk above that. There might have been some battery acid leak in the past and it ate through the metal or exposed it enought for air/water. Also water can come from above the battery from a few places. The key is do you have water comfing from that hole when it rains, maybe a hose test to confirm as when it rains, you can have water coming from all angles, including the outside of the car.

[King Mufasa]

you should pull the trunk carpet back and check the strut mount towers. They are known to rust up and bring in water.

[ELVA164]

Also, the vent on the side of the trunk under the rear bumper can allow water to gather in that tray on either side of the car.