Minecraft wiki entry for Gathering_resources_on_peaceful_difficulty, associated text: Wet sponges can be obtained as a drop from elder guardians on Easy, Normal, or Hard, or in the sponge room(s) in ocean monuments in all difficulties, including Peaceful. Although wet sponges are technically not renewable, the primary use of sponges is to soak of water, and when they are broken, the water is still drained. Because of this and the fact that wet sponges can be placed in the nether or cooked in a furnace to become a dry sponge all over again, sponges, despite them not being renewable, can be used an infinite number of times.