Minecraft wiki entry for Sponge, associated text: A sponge absorbs both flowing and source blocks of water up to 7 blocks away (taken as a taxicab distance) in all six directions around itself. Instead of a cube or a sphere, this effectively encloses the volume of an octahedron with vertices placed 7 units away from the center in each direction due to the game's extensive use of taxicab distance. A sponge does not absorb more than 135 blocks of water however, and water closest to the sponge is absorbed first. The absorption propagates only between adjacent water blocks and does not "jump over" non-water blocks, including air.