Love the comments! Now, to be to boring pedant with useless trivia…. in the original book, the stated reason the witch melted was because she was so old that she had utterly dried out and dusty, so the water washed all the rustiness away. Which means a young witch ought to be okay. Not sure of Baum‘s physics and/or chemistry here, but then, it is a land of talking scarecrows and tin men. And flying monkeys!