SpongeBob and Friends Find Atlantis

Plot
Thousands of years ago, the city of Atlantis is threatened by a huge tidal wave that will destroy the whole city. In order to protect the city, the queen of Atlantis offers herself as a sacrifice to The Heart of Atlantis, hovering above the city. The The Heart of Atlantis then surrounds the main part of the city with a force field-like shield, protecting it against the tidal wave as the city is sunk to the bottom of the ocean.

In 1914, Milo James Thatch (Michael J. Fox), an aspiring young linguist working in the boiler room at the Smithsonian Institution in Washington D.C., believes that a manuscript known as the Shepherd's Journal will lead to the location of Atlantis. When his request to lead an expedition is denied by the Institution's board, he finds himself contacted by millionaire Preston B. Whitmore (John Mahoney), a friend of Milo's late grandfather, Thaddeus Thatch. The elder Thatch had already located the Journal, and asked Whitmore to give it to Milo “when he was ready.” Whitmore asks Thatch to become part of a team to search for Atlantis on a high-tech submarine led by Commander Rourke (James Garner) and his second-in-command Helga Sinclair (Claudia Christian). The team’s sub is sunk by the Leviathan, a huge, ancient mechanical lobster-like monster. The team escapes with heavy casualties, and find their air pocket entrance to Atlantis. Just before reaching Atlantis, Milo accidentally sets the camp on fire, causing the crew and all their remaining vehicles to fall to the bottom of a dormant volcano that, though it is blocked up at the top, could provide a route to the surface. To their amazement, the city still survives in a bubble beneath the earth.

Atlantis’s princess, Kidagakash (Cree Summer) (nicknamed “Kida”) greets them and brings them to her father, the king of Atlantis (Leonard Nimoy), who initially refuses to let them stay, but eventually allows them to stay one night. Kida takes Milo on a tour of the city, and they explore an underwater mural which leads Milo to discover that the Heart of Atlantis, which he originally believed to be a power source, is also what is keeping the whole city alive. When they resurface from the mural, however, Milo finds out that the crew intends to take the Heart of Atlantis to the surface and sell it (thinking that it is some sort of crystal); when he refuses to work with them, Rourke forces Milo’s cooperation by threatening Kida’s life, Tigress, Master Shifu's student, throws Helga off to “lighten the load," and a Digimon monster uses its mouth to cut Rourke’s arm, crystallizing the commander.

The city safe once again. The crew prepares to return to the surface with riches given to them by the Atlanteans, but Milo, who has fallen in love with Kida, chooses instead to stay behind in the city. The team, once they return to the surface, and Mr. Whitmore come up with an alternative story to protect Atlantis’s secret and give Mr. Whitmore an Atlantean crystal;allowing him to be given the same life extending force that the citizens of Atlantis have. Milo and Kida, now king and queen of Atlantis, carve a stone likeness of the late king, which then ascends to join the other stone carvings of past kings circling the Heart of Atlantis (now once again open to the people of Atlantis, rather than hidden underground), and look upon the city as it begins to return to its former glory.