Lexa and Livi, the mermaid sisters, are excited to find a magnificent old shipwreck in the ocean. But what's even more fascinating is that they discover a treasure chest inside it! Together with their friends, they try various fun and unconventional ways to get the chest open, but nothing seems to work. Lexa thinks of giving up, but Livi is determined to open the chest no matter what! Will her perseverance win in the end? What will they find inside the treasure chest?