I really enjoyed day 17, but I got screwed over so badly because the example diagrams given are actually an edge case. The problem doesn't count ANY cells that are outside of the vertical range of the scan, including reachable cells that are above the first occurrence of clay. However, in the example the topmost cell that is reachable by water is already within range, making the number of reachable cells that you have to ignore 0.
I lost a lot of time with this puzzle because I didn't remove the topmost cells that are outside of the range of the scan, only the cells at the bottom.
Will eventually catch up with the other problems as well.