The Mismatched Tail and the Stars:

In an underwater city ruled by merfolk, a young inventor named Coral, with a prosthetic tail, stumbles upon a clue to a forgotten civilization. Fueled by curiosity, she convinces a prince to help her find the lost city of Lumina. Their discovery unlocks the secrets of a sustainable energy source, propelling Aquara into a new era. Generations later, Coral, now an elder, inspires a new crew to venture beyond their own star system, leading them to a groundbreaking discovery that holds the key to a future filled with exploration and harmony among the stars.