Harmony is chill. She is carefree and fun and loves to stop and smell the sea flowers. Echo is a worrier. She can always find something to fuss about. As her best friend, Harmony is determined for Echo to enjoy their debut performance in the Mermaid Ballet.

In a magical water world, the two mermaids practice their steps again and again. They dive through the water like seals, spin in circles like minnows, slither like eels, and more. But Echo is still worried that she'll forget everything as soon as she faces the audience. So Harmony decides that they should share a secret hand squeeze, one that tells Echo You are fine, you are okay, I'm right next to you. At the crucial moment when Echo is about to stumble, will their plan work so she gets all the moves correct?