J. K. Rowling works to dispel preconceived notions about magical worlds. With the merpeople, she does just that, in a wonderfully self-conscious way. She presents us with a beautiful, shapely, stereotypical mermaid in the painting in the prefects' bathroom, so we have a good idea of what Harry is to expect; then underwater, she reveals to us a village of hideous creatures with long, green, tangled hair, sallow gray skin, and broken teeth. They are not remotely what we thought Harry would find at the bottom of the lake, and they are not supposed to be, for even mythology must have its secrets, and even Harry, who is still learning about the wizard world, has his own, often misled, notions about how things should be.