Minecraft wiki entry for Drowned_farming, associated text: Drowned farms on the ocean floor are more complicated because they function similarly to a mob farm, capturing naturally-spawned drowned. First, the drowned should be attracted to one location. Once they are attracted, they need to be funneled into one area where the player can easily kill them. The attracting is often done with villager bait and the funneling is often accomplished with bubble columns.