A pale translucent blue, water fills pits so that it is usually level with the ground it is next to. It makes a continuous rippling motion, causing long, round waves. The waves sometimes cause it to rise above ground level.
Both sleepwalkers and nightmares will drown in water if they so happen to enter it. Water will stay in one place, and never move. Any sand poured on water will eventually come up to the surface, if the player continues to pour. This will create a platform that the sleepwalkers can use to cross.
In some levels, wooden platforms are located over gaps filled with water, and the player can use these to guide sleepwalkers without having to pour sand in pits of water, which can take a while for deep areas of water.