Minecraft wiki entry for Defense, associated text: Waterfalls are an effective way to protect your doorway as a last line of defense. By using an overhang, a player can run a waterfall down and over the entrance to their home. A one block deep ditch as wide as the waterfall will prevent the water from flowing in unwanted directions. If a creeper, skeleton, or zombie walks into the waterfall, they will be pushed down into the ditch, effectively stopping them. Though the ditch can be made deeper, it is inadvisable since the player may accidentally fall into the ditch themselves. The downward pressure of the waterfall will cause the player to swim upwards much more slowly than usual, so one block deep is recommended. To enter their home, a player must jump into the waterfall and keep moving forward. This will deposit the player safely on the other side of the waterfall.