Atlantica

Atlantica is a world appearing in all three Kingdom Hearts games. It is based on the setting of the 1989 film, The Little Mermaid.

Almost completely underwater, Atlantica is a rocky world with immense holes on its surface. Beneath the surface is an entire world full of fish, merfolk, and other aquatic species that make up King Triton's underwater kingdom. The Heartless that appear in Atlantica are unique to it, such as Sea Neons. In all games, the boss of Atlantica is Ursula (sometimes accompanied by Flotsam and Jetsam).

Setting
Atlantica has been the most drastically changing world throughout the Kingdom Hearts games. In each game its gameplay is completely different. In Kingdom Hearts, Ariel joins Sora as a party member and things carry out much like in any other world, with the exception that the controls are different to fit Sora's new form. In Kingdom Hearts: Chain of Memories, Sora doesn't change form at all, and the world is treated just like all other worlds. In Kingdom Hearts II, possibly the biggest change, only two areas are able to be traveled and does not further the story through gaming battles, but through songs.

Kingdom Hearts gives Atlantica a sprawling design that requires certain special abilities to navigate successfully. Sora and company arrive in the Tranquil Grotto, where Ariel and Flounder host the swimming tutorial. From there, the party travels forward, practicing battle in the Undersea Valley, following the trident marks to their final destination. One exit leads to the ironically-named Calm Depths, which plays host to a swift moving current that pushes Sora and his party around unless they use Ariel's dolphin friend or obtain the Mermaid Kick ability. Following the trident mark here takes the group to the Undersea Cave with a strong current of its own. Making it past the current leads to the Undersea Gorge, a vast area which leads to several other places in Atlantica. On the opposite side of the gorge are the entrances to Ariel's Grotto and, under the crate, the end of a hidden tunnel that leads to the Sunken Ship. Somewhere in the middle is the entrance to Triton's Palace and the Throne Room within. Also there, but easily missed, is the Undersea Garden, hidden to the left of the Palace entrance.

After getting into the Sunken Ship area, Sebastian helps the party find a hidden door in the corner which leads to the creepy Den of Tides; the right fork leads to the Cavern Nook, a room with a save point, while the left fork takes the party to the Tidal Abyss and, past that, Ursula's Lair for the first of two encounters with the sea witch. Finally, using Mermaid Kick from the Calm Depths, Sora and the party can reach the very end and find the entrance to the Open Ocean, where their final encounter with Ursula takes place.

Kingdom Hearts II features a tiny Atlantica in comparison; only two areas are available for Sora and the party to freely explore. They arrive and interact the most in the Undersea Courtyard, where the song mini-games are activated. On the opposite end from the save point is the entrance to Triton's Throne, which holds other characters, but no Heartless. It should be noted other locations in Atlantica are visited, but only as part of the song mini-games; they cannot be freely explored.

Kingdom Hearts
Sora, Donald, and Goofy arrive on this strange new world after being given new magical forms by Donald that will allow them to survive and adapt. They quickly meet up with Ariel, Flounder, and Sebastian. After teaching them to swim, the group is attacked by a group of Heartless, which Sora and his gang promptly dispatch. A concerned Ariel invites the group to visit her father's palace to see what to do. Taking them there, Triton dispatches more Heartless with his magic trident, dismisses Sora's questions about the world's Keyhole, and grounds Ariel. Sulking, Ariel sneaks off to her grotto, where she points out a mysterious mark on the wall. The party travels to the Sunken Ship, where they find a shining Crystal Trident that looks as if it might fit in the mark. After escaping Glut, a Great White Shark with a huge appetite, they take it back to the Grotto and place it on the wall, but before it can activate, Triton bursts in and destroys it. Ariel storms off, allowing Triton the opportunity to explain that he knows Sora and the rest are Keyblade bearers from another world. After proclaiming the Keyblade only brings destruction, he informs them they have no further business in Atlantica.

Meanwhile, Ariel is approached by Ursula, who promises the mermaid princess that she can help her get to "other worlds", but in order to do so, she needs Triton's trident. Ariel steals it and gives it Ursula, who uses it to injure Triton before retreating to her lair. Sora, Donald, and Goofy go in pursuit. Ursula escapes from her lair, but Ariel gives Sora a new power that will help him and the party get to Ursula and defeat her for good. Ursula receives a swift kick in the tentacles from Sora and his gang; they return the trident to Triton. He and Ariel open up the world's Keyhole, which Sora promptly seals.

Kingdom Hearts: Chain of Memories
Sora, Donald, and Goofy arrive in Atlantica based on their memories. They run Ariel who has stolen her father's trident to save her friend Flounder, who has been captured by Ursula to exchange for the trident.

They help Ariel rescue Flounder and eventually meet Ursula in a huge battle.

Kingdom Hearts II
Told through a series of five songs, the storyline basically follows the plot of The Little Mermaid film, with some intervention and assistance from Sora, Donald, and Goofy.

During the ending credits, Ariel is seen in human form and on a wedding ship with Prince Eric.

Character Design
Atlantica is unique in that Sora takes on a different form while on the world's "surface", courtesy of Donald Duck. While in Atlantica, he is transformed into a "dolphin merboy", while Donald himself becomes a half-duck half-octopus creature, and Goofy a sea turtle. It should be noted that this change of appearance does not take place in Kingdom Hearts: Chain of Memories or Kingdom Hearts: Re: Chain of Memories, and that while all the other residents of Atlantica (notably Ariel, Flounder and Sebastian) swim around, Sora is still seen running around in his red shorts.

Mini-Games
All gameplay during Kingdom Hearts 2 takes place during song mini-games, including the boss battle. Songs include:


 * Swim This Way
 * Part of Your World
 * Under the Sea
 * Ursula's Revenge
 * A New Day is Dawning

Kingdom Hearts II

 * There are no treasure chests in Atlantica.

Dalmatians

 * No dalmatians are found in Atlantica.

Trivia

 * Atlantica is one of the many few worlds to be shown with a change of day.
 * In addition to the above, Atlantica has had the largest world reduction, turning from an average sized world to just two areas. This is in direct contrast to Olympus Coliseum, which had the largest expansion, changing it from just three areas to the average size of a world.