is a 1983 Japanese animated science fantasy film and the fourth Doraemon feature film, released on March 12, 1983, in Japan. Directed by Tsutomu Shibayama, the film is based on the Western myth of Atlantis, the lost city. Plot The plot happens when the Bermuda Triangle is on the news. Meanwhile, Doraemon 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 Doraemon. That night, Gian and Suneo take Buggy and travel through the Atlantic Ocean, trying to find a treasure ship. But not realizing that the effects of the adaptation light can fade over time, they lose consciousness, and their friends, who have been looking for them, think they're dead, but they somehow wake up soon. They find the ship and Nobita, who is outside, sees a strange fish shaped craft that started attacking him with an energy weapon. He managed to evade it, but the others didn't believe his story. That night, Buggy wakes Shizuka and reveals he saw what happened with Gian and Suneo when they lost consciousness, showing his memory like a movie projector. The footage shows a strange underwater craft that's controlled by two human like figures. Soon, everyone else watches the footage as well, seeing these "Sea men" saving Gian and Suneo with their own Adaptation Light, before the craft Nobita saw appears and starts attacking them. Not long after, a giant squid appears and attacks the group, breaking their camp, but a strange light knocks the creature out. The group then sees the Sea men in front of them, but they too were knocked out by the stunning light. Nobita, Doraemon, and Shizuka later wakes up in a room where they meet one of the sea man called Eru, revealed to be inhabitants of the underwater kingdom of Mu. The Prime Minister of Mu welcomes the group, but doesn't allow them to leave due to the kingdom not wanting humans to know about their existence. While Gian and Suneo are put in a cell, the group rescues them and flee the kingdom, with Eru realizing their escape and giving chase. Doraemon