Conservation conflicts with social emotional lessons in Idle's plot. The concept that coral reefs suffer when the fish, sharks, and rays who live in them leave is clear, but the friendship narrative obscures the real reason why these creatures leave, such as pollution. Reading the book purely from a social-emotional level is problematic: everyone should be able to have time and space to themselves, and, unlike in the story, even best friends need to learn to give each other space.

Idle's illustrations, however, are utterly gorgeous and make the book worth a read in and of themselves. Just be prepared to give kids some adult guidance.