Pokémon Season 1 Episode 7

The Water Flowers of Cerulean City
In his quest to collect Gym Badges, Ash heads for Cerulean City, intending to confront the Cerulean Gym Leader. For some reason, Misty expresses a desire to avoid Cerulean City and disappears along the way. Upon entering the gym, Ash and Pikachu are entranced by a synchronized swimming show being performed by three beautiful sisters, unsure if he has really found another Gym. The three reveal that they are the Gym Leaders but have since converted the Gym into an aquarium and water show, and offer to just give Ash the badge, but Misty appears once more, revealing that she is also one of the Gym Leaders and will battle Ash in lieu of her three older sisters. However, Team Rocket disrupts the battle in an attempt to steal all of the Gym’s Pokémon, and Misty’s sisters decide to award Ash the Cascade Badge for helping save everyone.