Clean Water is the main liquid that you want to get to Swampy's bathtub.
You can also get Swampy Ducks with 5 drops of water. When at least 20 drops of Water gets in Swampy's bathtub, you complete the level. When Water gets on Cranky's food with algae, you fail the level. Clean Water will also destroy Cranky Ducks, but it has no effect on Allie Ducks. Water in this game has top notch physics, and can be contaminated by Poison Water and can destroy Toxic Ooze.