Sito, a mermaid boy with green scales, and Lila, a mermaid with red hair and a blue tail, become friends in their underwater world. One day, they meet Ozeana, a majestic blue whale, who takes them to Aqualandia, a fantastic kingdom at the bottom of the ocean. There, they play with strange and funny sea animals, discovering incredible wonders. After a magical day, Ozeana takes them home, leaving Sito and Lila with unforgettable memories and the promise of new adventures to come.