Ariel is a curious mermaid who has always wanted to explore the human world. After saving a prince named Eric from a dangerous shipwreck, Ariel makes a deal with the sea witch, Ursula, so she can meet him and learn more about what life is like beyond her ocean home. But Ursula is full of tricks, and it will take all Ariel's courage to save the human world and the ocean from the sea witch's devious plans.