During summer vacation, Nobita and his friends went to the bottom of the ocean waters in the Pacific Ocean. Giant and Suneo bring underwater vehicles belonging Doraemon and walk through the Atlantic Ocean, they are trying to find the treasure ship. Along the way, they realized if all the equipment Doraemon they carry out of energy all, consequently they were in danger. Fortunately, they were rescued by some sea creatures. Doraemon and his friends who were then captured by these creatures, revealed to be inhabinats of the underwater kingdom of Mu.

This suggests that other kingdom beneath the sea, Atlantis, which is now controlled by a robot, and will destroy the earth with nuclear weapons that they make. With the help of a young boy from Mu, Nobita and his friends tried to stop the robot, but all were arrested. However, when things were at their grimmest, vehicle underwater robot Doraemon's sacrifice himself to destroy the computer that controls all the robots and nuclear weapons. After returning to Mu, Doraemon and his friends regarded as heroes ...