Minecraft wiki entry for Drowned_farming, associated text: Some farms incorporate innovative ideas such as bubble-column elevators to bring items to surface level, and devices to sort items. The player can circumvent the hostile mob cap (but not the maxEntityCramming gamerule) by pushing the attracted drowned into the Nether dimension. If the Nether dimension is unusable for this purpose, then the bubble columns can transport the drowned up to the player's AFK spot, typically high in the sky.