King Triton and his wife, Queen Athena, rule over the underwater kingdom of Atlantica, filled with music and laughter. They have seven young daughters: Aquata, Andrina, Arista, Attina, Adella, Alana, and the youngest of whom is Ariel. One day, the merpeople relax in a lagoon above water, and Triton gives Athena a music box. However, a pirate ship approaches. Everyone escapes except Athena, who is crushed to death by the ship when she tries to rescue the music box. Devastated by the death of his wife, Triton throws the music box away, and music is banned from Atlantica.
Ten years later, Ariel and her sisters live under a strict routine maintained by their governess, Marina Del Rey and her assistant, Benjamin. Marina dislikes being the girls' governess and longs to be Triton's attaché, a job currently filled by Sebastian the crab. Ariel hates their current lifestyle, which brings her into arguments with her father. Ariel encounters Flounder, whom she later follows to an underground music club. She is overjoyed by the presence of music, and is shocked when she sees Sebastian performing there. When her presence is revealed, the entire band stops playing and hides, believing Ariel will tell her father about them. Ariel sings a song explaining her love of music and the remembrance of her mother, and she joins the club with an oath.
Ariel returns to the palace, and her sisters confront her over her disappearance. She explains where she was, and the following night the girls go to the club to have fun. Marina finds them, she later reports their activities to Triton, who destroys the club with his trident. Sebastian, Flounder, and the band are sent to prison, while Marina gets the job she wants. Triton punishes his daughters inside the palace, resulting in Ariel asking him why music is forbidden, but he refuses to answer and angrily shouts, "I will not have music in my kingdom!" Distraught, Ariel argues that her mother wouldn't have wanted music forbidden. She swims to the bedroom, with her sisters following. That night, she frees her friends and leaves Atlantica. Sebastian leads them to a deserted place far from the palace where Ariel finds Athena's music box, as Sebastian hoped. Ariel, Flounder and Sebastian decide to return to Atlantica to bring the music box to Triton, hoping that it will change his mind, as he has not remembered how to be happy after Athena died.
On the way back, they are confronted by Marina and her electric eels. Marina wants to stop them so she will retain her position of power, and a struggle ensues. Marina barrels towards Sebastian, but Ariel pushes her away, getting hit in the process. Triton arrives in time to witness this, and blames himself. He sings the lyrics of "Athena's Song", and Ariel recovers. Triton restores music to Atlantica, and appoints Sebastian as Atlantica's first official court composer, much to everyone's delight. Everyone rejoices except Marina who is sent to jail.Jodi Benson as Ariel
Samuel E. Wright as Sebastian and The Narrator
Jim Cummings as King Triton and Shelbow
Sally Field as Marina Del Rey
Parker Goris as Flounder
Tara Strong as Adella and Andrina
Jennifer Hale as Alana
Grey DeLisle as Aquata and Arista
Kari Wahlgren as Attina
Jeff Bennett as Benjamin the manatee and the Swordfish Guards
Andrea Robinson as Queen Athena (singing voice)
Lorelei Hill Butters as Queen Athena (speaking voice)
Rob Paulsen as Ink Spot the octopus and Swifty the shrimp
Kevin Michael Richardson as Cheeks the blowfish and Ray-Ray the manta ray
The film was produced by Walt Disney Pictures and DisneyToon Studios, animated by Toon City Animation, Inc., to the formerly Walt Disney Animation Australia, unit director Pieter Lommerse, workbook supervisor Stephen Lumley, clean-up director David Hardy, inbetween director Miles Jenkinson, effects director Marvin Petilla, supervising color stylist Jenny North and Aaron Stannard. The film's working title was The Little Mermaid III, and it was originally scheduled for a mid-2007 release. When John Lasseter took over Disney Animation, more resources were spent on completing Cinderella III: A Twist in Time, and attention only returned to this film in July 2006 after the wrap up of Cinderella III.
A teaser trailer and musical preview of the film (an alternate version of "Jump in the Line") were attached to the Platinum Edition DVD of The Little Mermaid, which was released in October 2006. At the time, the working title The Little Mermaid III was still being used.
The score to the film was composed by James Dooley, who recorded the score with a 72-piece ensemble of the Hollywood Studio Symphony, as well as a big band, at the Sony Scoring Stage. The film features new songs written by Jeanine Tesori, along with covers of previously recorded calypso songs that were arranged by Dooley. No soundtrack has been released yet for the film.
The songs featured in the film are:"Athena's Song" - Performed by Andrea Robinson (Queen Athena)
"Just One Mistake" - Performed by Sally Field (Marina Del Rey)
"I Remember" - Performed by Jodi Benson (Ariel)
"Jump in the Line (Shake, Shake, Shake, Senora)" - Performed by Samuel E. Wright (Sebastian) and chorus
"Jump In The Line" (Shake, Shake, Shake, Senora) A cappella version - Performed by Parker Goris (Flounder), Samuel E. Wright (Sebastian), Jodi Benson (Ariel) and chorus
"Man Smart, Woman Smarter" (instrumental only)
"Just One Mistake" (reprise) - Performed by Sally Field (Marina Del Rey)
"I Will Sing" - Performed by Jeannette Bayardelle
The film was released on Region 1 DVD in the USA on August 26, 2008, and on Region 2 DVD in the UK and Europe on September 22, 2008. The DVD contains special features including deleted scenes, a production featurette hosted by the director, games and activities, and a featurette hosted by Sierra Boggess about the Broadway musical.
On December 16, 2008, the film was released in a "The Little Mermaid Trilogy" boxed set that includes The Little Mermaid (Platinum Edition) and The Little Mermaid II: Return to the Sea. On November 19, 2013, it was released on Blu-ray as a 2-movie collection alongside the sequel.
The DVD became the top-selling DVD for the week ending August 31, selling 980,237 copies. Reviews of the film from audiences were largely positive, though the film received mixed to negative reviews from critics (33% on Rotten Tomatoes based on 6 reviews). The new villain, Marina Del Rey, has been criticized as being a poor follow-up to Ursula. The animation quality of the film has been praised as being "impressive" for a direct-to-video and comparable to that of the original film. A mildly negative review has described that in the film "goofiness often gets buried too often underneath a blah story that's much too run-of-the-mill to allow the emotional oomph of the characters' plights to truly impact". The music has also been criticized as being unmemorable, with one review stating that "to label this a musical would be false advertising".
In the United Kingdom, the word 'spastic' was cut from an interactive game in the extra features of the DVD and Blu-Ray releases by the BBFC to achieve a 'U' rating. An uncut version was available rated '12'.
The word however appears uncensored in all versions of the full-length feature.