Dive in and learn about an important Jewish holiday in the latest undersea outing from the author of the Pout-Pout Fish series.Mr. Fish has been invited to celebrate Passover with his friend Miss Shimmer and her family. The day before the holiday, Mr. Fish offers to babysit Miss Shimmer's niece and nephew while she goes shopping for dinner ingredients. He and the fry clean the house (apparently a coral cave) of chametz crumbs, turning the task into a fun Passover treasure hunt, before Miss Shimmer's elderly parents arrive bearing Haggadahs and special Passover tableware. Then Miss Shimmer returns and Mr. Fish helps her cook the Passover meal. The following night, at the seder, the Shimmers educate Mr. Fish about the history of Passover and the holiday's traditions, from the symbolic foods on the seder plate to the hiding of the afikomen and more. Children attending their first Passover seder may find the ritual a little easier to understand after reading this book, but some details don't add up; for example, how do the piscine characters perform the ritual of dipping spring vegetables in salt water when their whole world is salt water? The text sometimes feels too didactic, but occasionally there is a striking turn of phrase, such as when the Haggadah is poetically described as a "treasure map." Hanna's cheerful cartoony illustrations are functional.Affirming for Jewish readers and useful for those who feel at sea about Passover. (stickers) (Picture book. 2-5)