Ash and his friends are heading their way towards Viridian City for Ash's last badge. Meanwhile, Horsea is in the pool looking ill. Brock suggests that Horsea needs to swim in a bigger tank. Misty says that there is a big pool in the Cerulean Gym. So our heroes decide to go to Cerulean City for some fun. Misty calls up her sisters telling them that she is going to visit.

They have now arrived at the Cerulean Gym. Before they go inside, Brock sees a bulletin starring a mermaid and her Pokémon. Ash comments on how the mermaid looks almost like Misty. So they all go inside and Misty's sisters come out to meet her. Her sisters also go over to meet Ash and Brock. While everyone is greeting each other, Misty goes over to the pool and let Horsea out into it. Misty's sisters runs over to her and tells her that they have to rehearse for the Underwater Ballet. Then they tell Ash and Brock that Misty is the star of the show.

Daisy tells Misty that they were losing people for the audience and so they are trying something new. Misty doesn't want to be the star. Her sisters tells Misty that the show has already been advertised. They plead to Misty and they tell her that the frist show is tomorrow. Misty finally agrees to be a part of the show.

Togepi is walking on the edge of the pool. Pikachu tries to rescue it. Togepi regains its balance again and Pikachu falls into the pool. They start the rehearsal. The sisters tells Misty the story and what to do. Team Rocket is outside looking at the bulleting for The Magical Mermaid. They notice that water Pokémon will be in the show and Jessie suggests that they go and get tickets.

The next day, a long line waits for the show. Daisy is the cashier who is collecting the money from the people. Ash and Brock are in the audience waiting to see Misty. Misty is backstage looking at all the people in the audience. She tells Seel that she's a bit nervous but has confidence in herself. Daisy announces that the show is about to start. The tank comes up and everyone seems stunned by the cool effects. Misty dives into the pool and she plays with the water Pokémon. She starts off with a Seel and Goldeen and Seaking surround them. Misty goes into a cave with she can get air. She takes a deep breath and heads back down again.

Violet and Lily are backstage watching the show. Suddenly, Team Rocket appears and they want to be the villians for the show. Violet and Lily are afraid. The show continues on. The Pokémon and Misty begin to drift off to sleep. Then the light flashes and Team Rocket is seen in their costumes. Ash and Brock immediately notices them. Team Rocket dives into the water and they say their motto. The crowd is amazed at Team Rocket's performance. Then Meowth presses a button and their balloon bursts through the ceiling. Jessie and James throws a net at the water Pokémon. Misty tries to pull them back.

Now it is Daisy's turn to come on stage. Before she can, Ash and Brock tell Daisy that there are real villians out there. Brock tells Daisy to hold Togepi and Ash and Brock jumps into the water. In a nearby locker, Violet and Lily come out with tape over their mouths and with rope over their hands. Ash, Brock, and Pikachu dive into the water to stop Team Rocket. Jessie sends out her Arbok and Misty sends out Horsea. Horsea uses Bubble but Arbok justs destroys the bubbles with its tail. Horsea uses Smokescreen so that Arbok can't see. Suddenly, Seaking comes out and it pecks Arbok with its horn. James sends out Weezing for battle. Weezing automatically faints because it ran out of breath. Violet sends out her Psyduck. Of course Psyduck can't swim and so it hangs on for life. The audience laughs at Psyduck.

Ash sends out his Squirtle and he commands it to use Tackle. Misty tells Starmie to attack Arbok as well. Both attacks hurt Arbok. Jessie orders Arbok to attack the Pokémon. Before Arbok can hurt the Pokémon Seel gets in the way. Seel swims around Arbok and uses Headbutt. Misty tells Seel to use Aurora Beam on Arbok. Suddenly, Seel evolves into Dewgong! The audience claps for Dewgong. Ash looks up Dewgong in his Pokédex. Arbok begins to attack Dewgong but Dewgong easily dodges the attacks. Then Dewgong uses Ice Beam and it freezes up Team Rocket. Ash gets the Pokémon to safety and he tells Pikachu to really make this Thunderbolt count. Pikachu uses Thunderbolt and Jessie and James blasts into the air. Dewgong hits them and they head straight for Meowth and the balloon. All of Team Rocket blasts right out of the gym.

The audience claps and cheers loudly. In another room, Daisy tells Ash and his friends that their shows are already sold out. Since they don't have enough Pokémon for the show, they ask Misty if they can borrow hers. Misty gives them her Horsea and Starmie. Then they say goodbye and our heroes are off to Viridian City.

English Official Summary

One of Misty's water Pokémon is in desperate need of exercise, so the gang decides to take her Horsea to a gym that's run by her sisters in Cerulean City. But, Misty gets more than she bargains for when she learns that her sisters are planning an exciting underwater ballet.

Italian Official Summary

L'Horsea di Misty ha tanto bisogno di allenamento e i nostri eroi decidono di portarlo alla Palestra di Celestopoli (Cerulean City) dove le sorelle di Misty stanno preparando uno spettacolare balletto subacqueo!

Portuguese Official Summary

O Horsea de Misty precisa desesperadamente de exercício, pelo que o grupo decide levá-lo ao Ginásio das irmãs dela na Cidade Celeste. Aí, ela fica a saber que as suas irmãs estão a planear um empolgante "ballet" subaquático.

Spanish Latin America Official Summary

El Horsea de Misty necesita ejercicio desesperadamente, y los chicos deciden llevarlo al Gimnasio de sus hermanas en Ciudad Celeste. Ahí, ella descubre que sus hermanas están planeando un emocionante ballet bajo el agua.

Spanish Official Summary

Uno de los Pokémon de tipo Agua de Misty necesita desesperadamente hacer ejercicio, de modo que la pandilla decide llevar a su Horsea a un Gimnasio que dirigen sus hermanas en Ciudad Celeste.

English Great Britian Official Summary

One of Misty's water Pokémon is in desperate need of exercise, so the gang decides to take her Horsea to a gym that's run by her sisters in Cerulean City. But, Misty gets more than she bargains for when she learns that her sisters are planning an exciting underwater ballet.

Dutch Official Summary

De Horsea van Misty heeft dringend uitdaging nodig, dus brengen onze helden hem naar de Gym van haar zussen in Cerulean City. Daar ontdekt ze dat haar zussen een spannend onderwaterballet aan het voorbereiden zijn.

French Official Summary

L'un des Pokémon Eau d'Ondine a un grand besoin d'exercice, alors le groupe décide d'emmener l'Hypotrempe à l'Arène d'Azuria, qui est dirigée par les sœurs d'Ondine.

German Official Summary

Eines von Mistys Wasser-Pokémon ist ganz aus der Übung. Daher entscheidet die Gruppe, das Seeper in eine Arena zu bringen, die von Mistys Schwestern in Azuria City geleitet wird.

Danish Official Summary

Mistys Horsea har desperat brug for at træne, så vore helte beslutter sig for at besøge Mistys søsters sal i Cerulean City. Der erfarer hun, at hendes søster er ved at opsætte en spændende undervandsballet.