Picture would help, but brown water is water passing thru wood. I have seen water go 20' from where it entered. If your deck slopes, it could come from the front of the cabin, windows or ports, and so on. It usually takes a very close inspection of the cabin above the leak point. As a screw loosens over time, water can go down the threads. When I drive screws in wood or cored decks, I squirt epoxy in the pilot hole before driving.