The idea behind Finite Liquid is to “fix” Minecraft‘s weird water physics (sans the oceans, which remain the same). With this mod, popping a hole in something containing water will cause it to drain out, and as the mod author notes, if you knock a hole between a lake and a cave, the cave will flood (and the lake will drain). What’s more, the mod lets you drop pipes and actually pump liquid around, boil water (it can harm other creatures — think mod traps), use grates to control liquid flow, sop it up with sponges and even build diving gear to explore underwater milieus.
Get it: Finite Liquid