Maia's Mermaid Friend (paperback)

Maia is going to the race, but it's early. She stops to look at her reflection in the pond. The reflection turns into another girl -- a girl who is swimming -- a girl who is a mermaid named Trezzie. Trezzie takes Maia's hand and together they swim to her castle under the water. She gives Maia a piece of a plant that becomes a doorbell, so Maia can call her any time. The two of them skip stones across the water. Maia's friend Fig shows up. "Where were you? Why weren't you at the race?" Maia tries to explain she was swimming with her new friend Trezzie. Fig can't see Trezzie and doesn't believe her. Fig goes away mad. Trezzie resurfaces. Maia and Trezzie continue playing.