Minecraft wiki entry for Drowned_farming, associated text: The simplest way to start a survival-mode drowned and zombie farm is to locate a dungeon room that contains a zombie mob spawner. Ideally the room should be reasonably close to the overworld surface, but can be any depth that allows for digging 5 blocks or so underneath the floor. Sometimes a dungeon is found a short distance inside a cave entrance. Unlike an XP farm that generally requires a long falling distance from the dungeon to bring the mobs to near death, no deep excavation is required for a drowned farm.