Dynamic:
Wow. That is a lot of water accumulated in that door. Your friend should be grateful that you caught it. I've seen wet cars that were closed up for a couple of weeks that were full of mould.
Coincidentally, my 9 year old Outback started leaking inside on Friday. Sunroof drain channels seem to be the culprit.
I hope he's grateful, because I'm bloody over working on this car for him haha.