Minecraft wiki entry for Drowned_farming, associated text: In Bedrock Edition, mobs spawn in the range of 24-44 blocks from the player. In Java Edition, mobs spawn in the range of 24-128 blocks from the player. Building over deep ocean far from land allows for somewhat lower altitude. The killing platform where you wait for the drowned must be more than the maximum spawning range from any possible spawning location on land or in the ocean.