Water in trunk after heavy rain

Hi. I enlisted a cute assistant to help me find the leak-but I was the one that ended up in the trunk and she held the flashlight! I couldn't see any light shining thru. But the previous owner definitely tried to patch the rear window with some sort of blackish material. I can see that the corners of the bottom have gaps and inside the trunk the left quarter panel has some rust colored tracks. I think I will head to a glass shop and see if they can reseal it, I don't think I want anyone removing the glass-not just yet!