Chunk of dripstone, Dripstone grates.

A chunk of dripstone can be gotten by destroying some of the stalagmites/stalactites which can be used, along with iron, to craft a dripstone grate. A dripstone grate can be used as a physical barrier for entities and players but not for water. Much like a drain, water will flow through the grate and come out on the bottom side of the block.This block can be used to let water flow through walls, ceilings or floors, depending on the orientation the grate is placed in.  This also ties into the fact that dripstone can absorb and drop down water.