In the underwater kingdom of Atlantica, a free-spirited mermaid princess named Ariel grows tired of the monotony of her life. Frustrated with the limitations imposed upon her by her father, King Triton, and the expectations of her overprotective but well-meaning sisters, Ariel yearns for adventure and freedom. With a taste for the unknown and a curiosity that often gets her into trouble, Ariel spends most of her days exploring the ocean, dreaming of the world above the waves. Ariel's fascination with the human world is exacerbated when she stumbles upon a sunken ship, where she discovers a chest filled with human treasures. Among these treasures is a beautiful, golden comb, which she becomes infatuated with. The comb was originally owned by Prince Eric, a handsome and kind-hearted human prince who had been on the ship when it sank. Ariel becomes obsessed with the comb and, through her manipulation of her friend, the fish Flounder, manages to escape her father's watchful eye and visit Prince Eric's kingdom. During one of these visits, Ariel saves Prince Eric from drowning and this event inadvertently sparks their romance. The two share a deep attraction, and Ariel becomes determined to make her life with him on land. When Prince Eric auctions off his items from the sunken ship, Ariel sees this as an opportunity to make contact with him again. In her rush, however, she is detected by King Triton's advisor, Scuttle, a wise-cracking seagull who tries in vain to dissuade Ariel from pursuing her dreams. As Ariel and Prince Eric grow closer, Ariel's existence becomes increasingly difficult to conceal from her father. Fearing her daughter's safety and disapproving of her interaction with humans, King Triton sets Ariel up with a diplomatic meeting with Prince Eric, so as to arrange a royal wedding. But deep down, King Triton is aware of Ariel's infatuation with Eric and believes that her desire to be with him may ultimately lead to Ariel's doom. Meanwhile, a darker figure emerges from the depths of the ocean. The sea witch Ursula, King Triton's sister, had long sought revenge against him for stripping her of her rightful place as queen. With a long-standing grudge and an insatiable desire for power, Ursula begins to weave a sinister plot to overthrow King Triton and exploit Ariel's love for Eric to her advantage. Ursula makes a Faust-like bargain with Ariel, trading her beautiful voice for a pair of legs in exchange for her assistance in winning Prince Eric's heart. With her new human legs and voice, Ariel manages to win Prince Eric's heart, but things start to go awry. Unbeknownst to Ariel, Ursula has other plans. Once Prince Eric begins to show affection for Ariel, Ursula secretly takes control of his ship and sets it on course for a supposed 'love test'. Fearing her daughters' safety, King Triton allows Ariel to stay on land under the sole condition that she will return to her role as a princess once Prince Eric marries her. In a thrilling climax, Prince Eric thwarts Ursula's sinister plans and captures her right-hand, the shrimp eel, Flotsam, and Jetsam. Ariel learns the truth behind Ursula's intentions and returns to her life under the sea, hoping that she can make Prince Eric love her for who she truly is. However, fate conspires against Ariel once again as Ursula's eel servants trick Ariel's sisters into revealing the location of the Trident of Poseidon, a powerful artifact that can control the ocean and ensure the sea witch's reign. The eel pair then attempts to deliver it to Ursula. In a desperate attempt to retrieve the trident, Ariel faces off against Ursula in an intense sea battle, but ultimately is forced to hand it over to the sea witch. With the trident in hand, Ursula begins to control the ocean and its creatures while Prince Eric is captured by Ursula's eel minions. With her love life hanging in the balance, Ariel attempts to outwit Ursula and save Prince Eric, but Ursula proves too cunning and captures King Triton. Determined to save her father and Prince Eric, Ariel takes great risks and makes her enemies realize that she's ready to accept the consequences of her choices. Through some daring actions, Ariel is eventually able to defeat Ursula, shattering the mirrors of the sea witch's and restoring the Trident to her father. Ariel confronts Prince Eric at the church where he was initially supposed to marry another woman and successfully convinces him that he truly cares for her. Just as the wedding bells are about to ring, Ariel is seen returning her voice to its original state so she can reveal her true nature to Prince Eric. She does so by performing a heartfelt rendition of an iconic song calling out Ursula. Prince Eric falls in love with Ariel once more, and King Triton, with a newfound understanding and love for his daughter, finally embraces Ariel for who she is. The movie concludes with Ariel and Prince Eric riding off into the sunset together, while Ariel's sisters learn valuable lessons from their experience. As the underwater kingdom of Atlantica celebrates the reunion between love and family, Ariel finds a new, newfound appreciation for the harmony that exists between her two seemingly disparate worlds.