Minecraft wiki entry for Man-made_lake, associated text: You can make a lake any depth with ease! All you do is dig out your lake. (i.e. 6 blocks deep and also a rise near the edges) Then you do 1 layer of dirt where you want the water level to be. Fully cover the lake with the one block high layer and fill/overlap with water. (Make sure water becomes fully still/settled!) Grab a diamond shovel and with ease you dig up the top and only layer of dirt as your lake fills with water. You can also add to an already made lake like this, and just add 1 layer of dirt blocks at water lvl and watch as the waterfall extends over your extended lake. Once again you dig out the layer of dirt once you've gotten the water to settle.