Minecraft wiki entry for Mining, associated text: These are made by the same method as an underground base, except the open area is filled with water from artificial springs, lakes, rivers, etc. For additional effect, a lot of players build underwater bases from glass blocks, and build airlocks for extra stealth. Most quarries are square or rectangular, so it is hard to disguise an underwater base as a natural lake or pond, but with a little bit of work, they can be made to look like a natural body of water.