Doraemon: Nobita's Great Mermaid Naval Battle

The plot revolves around a summer vacation of Nobita and his friends under the waters of Pacific Ocean. Jaian and Suneo take Doraemon's underwater vehicle and travel through the Atlantic Ocean, trying to find a treasure ship. 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. Fortunately, they are rescued by some marine creatures. Doraemon and his friends are later captured by these creatures, revealed to be inhabinats of the underwater kingdom of Mu. 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, Doraemon's robotic underwater vehicle 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.

Finding a treasure is always been so hard! But, nothing is ever impossible for Doraemon and his magic tool. And so, with the help of Doraemon, Nobita and the rest of the gang set sail on a ship to find treasure on an islands. However on their way to the island, the ships have almost been destroyed and resulting Nobita to stray on an island with a young pirate while Doraemon and the rest of the gang somehow involved in a war between pirates.And so, their adventure begins...

Doraemon and its friends open a hole in the time and they're travel to the Country of Mayana, a lost Mayan civilization in the jungle. There, Nobita will know its perfect double, prince Thio, heir to the throne. Both will decide to interchange papers to try to save to the Country of Mayana of the claws of the infernal Ledina witch and her evil forces.

Nobita requests of Doraemon the Moshimo-box and wishes for the world to become a place where the use of magic is possible. Witchcraft replaces science and technology and everyone makes use of it on their daily lives, except for Nobita, who, like usual, isn't very good at conjuring spells. Frustrated, he plans on returning things to their past state, but his mother threw the Moshimo-box away. One day, Doraemon and his friends meet Professor Mangetsu, who studies magic and magical beings such as goblins, and his daughter Miyoko, and are warned of the dangerous approximation of the "star of the Underworld" to the Earth's orbit. With the future of the planet at stake, the group must travel to the Underworld and pierce the heart of the Underworld King with a silver dart, as detailed in the ancient texts of "The Chronicles of the Underworld". Their attempts are, however, thwarted and Miyoko captured. Doraemon and his friends then decided to use the Time Machine to return to the past and, using Dorami's Moshimo-box, they manage to restore the Earth. The events on the Underworld continue, however, to take place in a Parallel Universe, where Miyoko is still captive. As a result, the group is once again forced to travel to the Underworld and defeat its tyrannical ruler once and for all.