I don't know if anyone has posted this or not, but I came up with a different solution for the barrel part of the puzzle. To me it resembled the 5_1 bouy the most, so I took it to mean either 6 (5+1) or 4 (the number inbetween the 5 and 1 in the final solve for that puzzle, this would also cover 5-1=4). I ended up going with 6 for my "bouy" number. All the other numbers followed similar logic already mentioned in other posts.
I can't wait for the answer to post.