No matter how much rain comes down on it it won't get any wetter. What is it?

Why this works

The riddle plays on the paradox of water itself. While rain makes things wet, water is already the essence of wetness, so no amount of additional rain can make it "wetter." This clever twist highlights that water, by its very nature, cannot change its state of wetness regardless of the rain it receives. It's a fun way to think about the inherent properties of substances!