Sarah Mlynowski 
Sink or Swim [EPUB ebook] 
Book 3

In this fresh, funny new middle grade series, bestselling YA author Sarah Mlynowski writes for a younger audience for the first time! In each book, Abby and her younger brother Jonah visit the magic mirror in their basement at night, and the mirror transports them inside a different fairy tale. In the third magical adventure, Abby and Jonah find themselves splashing around with the Little Mermaid. But her story didn’t have a happy ending. This time, Abby’s determined to change things for the better!