Minecraft wiki entry for Water-powered_boat_transportation, associated text: To make channels wide enough to transport a boat, and remain on a level surface without changing elevation (elevation changes are described later), the water flow must be managed so that the channel can turn a corner, or keep moving in the same direction. The schematics below illustrate a method of creating a corner turn, and methods of extending travel in one direction by shifting the flow over a bit when the water runs out from the water source block.