I've already gotten all 64 cube/anti-cube bits in Fez and finished the game, but there are two doors which remain inaccessible to me. The 64-bit door under the little tree island, and the door underneath the main warp gate.
I've already reduced the flow at the waterfall, of course, but I can't find anything else which will allow me to lower the water a little bit more so I can reach these two rooms.
What do I do? I've looked through a dozen walkthroughs, to no avail!