The plot happens when the Bermuda Triangle is on the news. Meanwhile, Doraemon (character) and friends go camping after helping Nobita to finish his homework. They use an adaptation light to survive underwater, and an underwater buggy to commute. This buggy has feelings and likes Shizuka. Doraemon takes out a big tent that provides all their needs, and that night they have a barbecue, with Gian and Suneo wanting to go the Atlantic but disallowed by nobita. That night.Gian and Suneo take Buggy and travel through the Atlantic Ocean, trying to find a treasure ship. They lose consciousness, and their friends, who have been looking for them, think they're dead, but they wake up soon. They find the ship and doraemon, who is outside, sees a ea horse. Along the way, they discover that the environment gun that Doraemon used to protect them is running out of energy leaving them vulnerable to the sea. They are rescued by some marine creatures. nobita and his friends are later captured by these creatures, revealed to be inhabinats of the underwater kingdom of Mu (lost continent). It is revealed that another undersea kingdom, Atlantis, now controlled by robots, was about to destroy the Earth with nuclear weapons after mistaking a volcano eruption for an invasion. With the help of a young boy from Mu, Nobita and his friends attempt to stop the robots, but are all captured. However, when things are at their grimmest, Buggy sacrifices itself to destroy the computer that controlled all the robots and nuclear weapons. After returning to Mu, Doraemon and his friends are hailed as heroes before returning home.