Atlantica is a world of land and sea. Under the ocean is an entire civilization of merfolk and other sea creatures. Until his death about 25 years ago, this underwater kingdom was ruled by the steady hand of King Triton and his powerful trident. After his death, the trident was passed to the six eldest daughters of the late king, Aquatta, Andrina, Arista, Adella, Alana and Attina. Though the six sisters sometimes bicker, they rule together. They too, are now old and all together, there are 12 younger mermen and 8 mermaids that could possibly inherit the trident.

Triton's youngest daughter, Ariel, at age 16, made a deal with the sea-witch Ursula to become human. She was, after a significant amount of strife, married to Prince Eric, the ruler of the land of Atlantica. They had a daughter by the name of Melody.

At her christening, Melody was almost abducted by Ursula's sister, Morgana. To protect their daughter, Ariel and Eric built a wall to prevent her from venturing into the sea, but never the less, she becomes an avid swimmer. She discovers the magic locket that was to be her christening gift, which makes her visible to Morgana. Morgana tempts her by offering to turn her into a mermaid in exchange for the trident. After a good deal of trouble, Morgana is defeated and Melody unites the land and sea by tearing down the wall her parents built.

From then on, the merfolk and the humans have lived together. Melody and her husband, Corey rule the land, along with crown prince, Ron.

IMPORTANT: You can only explore places in the Underwater Kingdom if you can breath there, which can be accomplished through a magical transformation or magic of another kind.