Nani and her brother, Ikaika, go swimming at a beach shaped like the smile of the moon. Ignoring their mother's warning, they soon swim out much too far. Beneath the waves lies a giant eel who, before the children can stop him, grabs Ikaika by the leg and drags him to his underwater cave. Frantic, Nani turns to the sea creatures for help. One by one, each animal refuses her teary plea until, surprisingly, the smallest of them all meets the challenge and comes to the rescue proving that even the tiniest creatures can be the bravest.