With four badges, Ash can now make it to the Orange League competition. Tracey fills his water bottle with salt water. He tells Misty that he will use it for his research. Pikachu sees a big shadow beneath them. Ash and co. sees it too. The thing lifts up to the surface. It is revealed as a submarine. A man appears from the sub. He calculates a few things. The man sees Ash and co. and tells them that they will see a great thing. Ash wonders what the man is talking about. Misty wants to know what could happen. The waves starts to get rough. A big herd of Magikarp starts to swim on the surface. Tracey spots some colored bands on the Magikarp's tail. The man seems to know where the Magikarp is headed, and he heads off for that place. Tracey assumes that the Magikarp are headed for Rind Island.

Ash returns Lapras, and they decide to check the place out. They notice that the Magikarp are swimming upstream. The man comes up to the kids. He hands them each a bag to carry, and they follow him. Misty asks for the man's name. The man tells her that he is Quakenpoker. Quakenpoker tells her that everyone on his mom's side was named Quakenpoker. He says that he is a Pokémon Watcher and has dedicated his life to study Magikarp. Tracey is excited by this. A Magikarp jumps up and splahes Tracey. Quakenpoker tells them to stop fooling around because he has observations to make.

Ash and Misty thinks that Magikarp are very boring to watch. Quakenpoker sets up a machine. A paper prints out, and he looks at it. The machine tells how many Magikarp there are as they pass by. The machine also measures the Magikarp. Traey asks if Quakenpoker was the one who put the bands on the Magikarp. Quakenpoker tells him that he did. The Magikarp that left one year ago has a red band, two years ago is a blue band, and three years ago is marked with a yellow band. Quakenpoker tells Tracey that he must find this interesting because he is a Pokémon Watcher. Ash and Misty comments on how clever Quakenpoker is right now. Quakenpoker takes a look at Tracey's sketchbook. He sees a great future ahead for Tracey.

Team Rocket is shocked at the amount of Magikarp in the sea. James and Meowth decides to capture Pikachu. Jessie tells them to wait. She says that they can capture the Magikarp instead because they can evolve into Gyarados. With Gyarados, Team Rocket can become the greatest Pokémon Masters. James and Meowth likes Jessie's idea, and so they run for action.

Meanwhile, the Magikarp are swimming up a waterfall. Ash can't figure out the reason of why the Magikarp are doing that. Tracey tells him that all year the Magikarp are building up their strength so that they can reach the top. Quakenpoker adds in that only 50% of the Magikarp makes it up to the top. The others just keep on trying to reach their goal. At the top, Team Rocket appears with nets. James doesn't see the reason of why the can't use Pokéballs. Jessie says that Pokéballs costs money, which is something they do not have. James sees a Magikarp, and he catches it. It's a very big Magikarp. Suddenly, the Magikarp flops out of the net. Team Rocket grabs onto it, but the Magikarp flops back into the ocean, puilling Team Rocket in it. Team Rocket screams as they fall down the waterfall. Ash hears the screaming. Quakenpoker tells them that the Magikarp are going to evolve.

Ash wants to know when the Magikarp are going to evolve. Quakenpoker tells Ash to be patient. Some of the Magikarp aren't even going to evolve because they are not strong enough. They stop for a dinner break. Quakenpoker notices the strong relationship between Ash and Pikachu. Misty feeds Togepi some food. Quakenpoker tells her that Togepi likes to be petted on their front spike. Tracey never knew that Quakenpoker had knowledge on other Pokémon. Quakenpoker says that he likes all Pokémon, but Magikarp are his favorites. He says that he became interested because a Magikarp got stuck in his pajamas one day.

When Ash and Misty are asleep, Tracey and Quakenpoker discuss the Magikarp. Tracey holds out a picture and says that the Magikarp use the position of the sun to find their way back home. Quakenpoker tells him that the Magikarp who can't jump out of the water still manages to find their way back home. They both find Magikarp hard to understand. Ash and Misty wakes up. They see the Magikarp jumping out of the water. This means that the Magikarp can sense that something very exciting is about to happen. The water begins to get rough. Team Rocket's sub appears, and they begin to capture the Magikarp with the mechanical claws. Team Rocket is happy that they are getting a load of Magikarp. The large amount of Magikarp begins to fill up the sub fast. Soon enough, the sub begins to sink because the heavy weight. Ash and co. wonders where the Magikarp have gone to. Team Rocket's sub surfaces the water. Team Rocket gets out of the sub, and they say their motto. Quakenpoker demands Team Rocket to release the Magikarp. Jessie and James begins to throw the Magikarp out of the sub. Fortunately, Ash and co. catches the Magikarp before they hit the ground. While Ash and co. are distracted, Meowth captures Pikachu. Ash tells Pikachu to use Thunderbolt, but Quakenpoker reminds him that the attack would also shock the Magikarp.

Ash sends out Bulbasaur. Bulbasaur uses Vine Whip in order to grab Pikachu. Team Rocket tosses Pikachu to each other, so that Bulbasaur can't get Pikachu. Ash returns Bulbasaur. James looks up and sees a Magikarp stuck to his head. James desperately tries to get the Magikarp off, but he can't. Even Jessie and Meowth can't pull the Magikarp off of James's head. Quakenpoker helps James by treating the Magikarp with care. Magikarp lets go of James. Ash grabs onto Pikachu, and they jump off the sub. Suddenly, the Magikarp that Quakenpoker was holding glows. Everyone watches with amazement as the whole sea glows. The Magikarp are evolving. A twister is formed, and Team Rocket is trapped in the middle of it. Team Rocket is thrown across the ocean. Ash and co. watches as the Magikarp evolve into Gyarados. Quakenpoker needs Tracey to help him count the Magikarp and Gyarados. They watch as the Magikarp and Gyarados swim away from the island. When Quakenpoker and Tracey are done counting, Tracey reports that 70% of the Magikarp evolved. They thank each other for their hard work.

The sun begins to rise. Ash tells Pikachu that they can win the Orange League competition if they work hard. Meanwhile, Team Rocket has landed on a rock with a small group of Gyarados surrounding them.

English Official Summary

Ash and friends are no sooner recruited as assistants in an elaborate project researching Magikarp evolution than Team Rocket surfaces, stealing the object of the young Trainers' research.

Italian Official Summary

I nostri eroi si imbattono nel sottomarino di uno studioso che osserva i Magikarp e seguendolo vengono reclutati come assistenti nel suo progetto di ricerca sull'evoluzione di questi Pokémon. Ma il Team Rocket ha ben altri piani...

Portuguese Official Summary

Ao descobrir o submarino de um cientista no mar, nossos heróis se deparam com a pesquisa de sua vida: uma escola de Magikarp respingantes! Eles o ajudam a estudar a Evolução do Magikarp, mas a Equipe Rocket tem outras ideias.

Spanish Latin America Official Summary

Tras descubrir el submarino de un científico, los chicos se ven rodeados de la investigación de su vida: un banco de Magikarp. Quieren ayudarlo a estudiar la Evolución de los Magikarp, pero el Equipo Rocket tiene otra idea.

Spanish Official Summary

Ash y sus amigos son reclutados como asistentes en un laborioso proyecto de investigación de evolución Magikarp, justo cuando el Team Rocket aparece y roba el objeto de investigación de los jóvenes Entrenadores.

English Great Britian Official Summary

Ash and friends are no sooner recruited as assistants in an elaborate project researching Magikarp evolution than Team Rocket surfaces, stealing the object of the young Trainers' research.

Dutch Official Summary

Onze helden vinden de duikboot van een wetenschapper op zee, en ontdekken een school spetterende Magikarp! Ze willen de wetenschapper helpen met het bestuderen van de Magikarp Evolutie, maar Team Rocket heeft andere plannen.

French Official Summary

Sacha et ses amis sont recrutés comme assistants dans un important projet de recherche sur l'évolution de Magicarpe, mais la Team Rocket ne tarde pas à faire surface pour voler l'objet d'étude des jeunes Dresseurs.

German Official Summary

Ash und seine Freunde sind gerade zu Helfern für ein wissenschaftliches Projekt zur Entwicklung von Karpador ernannt worden, als Team Rocket auftaucht und ihnen ihr Versuchsobjekt stiehlt.