Minecraft wiki entry for Building_water_features, associated text: Swimming pools come in all shapes and sizes, so a lot of what a swimming pool looks like is up to you. One trick that is necessary when building 2, 3, and 4 block deep swimming pools, is in order to put water sources in every empty space, start by digging only 1 down for every block, and put the water layer there. Then, for the deeper parts, dig however many blocks down you want that part of the pool to be, and the water should flow down.