What happens when you throw water on a witch?
Since witches were believed to have spurned the sacrament of baptism, it was thought that the water would reject their body and prevent them from submerging. According to this logic, an innocent person would sink like a stone, but a witch would simply bob on the surface.
Who threw water on the Wicked Witch?
She is killed when Dorothy throws a bucket of water on her, in attempt to put out a fire the witch bestowed on the Scarecrow. In the novel, Dorothy simply throws it on her in a fit of anger.
How did the Wicked Witch melt?
It wasn’t the water that melted the Wicked Witch, but the act of kindness behind it. When she caught fire Dorothy instinctively tried to help her despite everything she had done, and being a creature of pure wickedness that level of kindness is fatal.