As our friends quietly sit on the foreshore of a nearby river, Ash is seen polishing his Pokéballs. Ash believes that in becoming the world’s greatest Pokémon trainer, he is a firm believer in Pokéball maintenance. After finishing polishing his ‘regular’ Pokéballs, Ash must take special care of the GS ball. Just as Ash begins to start with the GS ball, Brock finishes preparing lunch. But before our friends have a chance to eat anything, a strange looking Pokémon pops its head out of the nearby river. Ash pulls out his Pokédex and asks Dexter what it is: “Quagsire, the water fish Pokémon. The Quagsire makes its home in clean fresh water lakes. The Quagsire is covered by a slippery layer of skin making this Pokémon especially difficult to handle”. As Misty is a lover of water Pokémon, she finds Quagsire extremely cute and wants to capture it, but as she is about to release one of her stronger, more highly trained Pokémon, Psyduck appears. After a bit of a staring contest, Quagsire emerges from the water and grabs Ash’s GS ball and swims up the river. Our heroes give chase but they cannot keep it with this slippery Pokémon, so Ash uses Squirtle to catch Quagsire but due to its slippery skin, Squirtle cannot hold on. Not willing to give up, Squirtle again gives chase but as he is about to catch up, Quagsire uses his tail to whack him away. After hitting Quagsire on the back of the head with Squirtle’s water gun attack, Quagsire drops the GS ball and Pikachu catches it. After Squirtle and Quagsire have a brief water gun battle, Officer Jenny appears on her motorcycle. She then arrests our friends for violating the Quagsire Preservation Restrictions.
Once back in the police station, Professor Oak pleads our friends innocence as he forgot to tell them about Cherry Grove’s strict Quagsire laws. Cherry Grove City apparently uses the Quagsire to judge how pure their water sources are as they only live in the cleanest of water. Ash, after finishing talking with Professor Oak, wonders why the Quagsire had stolen his GS ball. Officer Jenny, in response, tells Ash that the Quagsire probably took it because it was round. Around this time every year, the Quagsire appear looking for anything round and they swim back upstream to their home at Blue Moon Falls. The next morning, the things taken float back down the river and their owners reclaim them. CherryGrove City considers it good luck; especially of the owners is the last one that comes back.
Quagsire then appears outside the police station window, still after the GS ball. Ash however is not willing to let it go and Quagsire looks rather upset. After walking back through town, our friends journey across a bridge and see a different Quagsire unscrewing a shiny ornament from the bridge. Suddenly, Quagsire appears and jumps on Ash, trying to get into his back pack in search for his GS ball. Ash chooses Chikorita to lend him a hand, but she panics when she sees Ash being attacked by Quagsire so she uses the leaf on her head as a kind of windmill and knocks everyone over. Brock then tells Ash that Chikorita has become a little overprotective, as she appears to have a crush on Ash (very funny). Meanwhile, Quagsire is still on Ash’s back and Chikorita spots him. As Chikorita attacks with her windmill thing, the GS ball falls from Ash’s bag and Quagsire swims off with it. Ash attempts to give chase but Chikorita grabs hold of his leg and he falls to the ground.
In another part of town, Meowth is playing with a round ornament he found in a nearby field (looks like the one the Quagsire had taken from the bridge). James, pretending to be a fortune teller, gazes into the ‘crystal ball’ and attempts to find out where the “twrips” our hiding. But out of nowhere, a Quagsire’s reflection appears on the ball and takes his ornament back. Just as James and Jessie were about to free Arbok, Victreebel and Lickitung, three other Quagsire appear and take their Pokéballs.
Meanwhile, our heroes after losing Quagsire come across the Quagsire that had stolen Team Rocket’s Pokéballs and they decide to follow them hoping that they will lead them to the Quagsire which took their GS ball. Ash, Misty and Brock then see a whole bunch of Quagsire and Ash decides to capture the one who stole his ball. Misty however quickly stops Ash and reminds him what Officer Jenny had told them. On the other side of the lake where the Quagsire are swimming, Team Rocket spot our friends and decide to steal all of the Quagsire. As the gradually descend in their balloon, they try to capture the Quagsire one by one with these mechanical claws but the Quagsire is too slippery and they quickly escape. Team Rocket then uses a net to capture all of the Quagsire. They then use the mechanical claws to grab hold of Pikachu. But before they have a chance to escape, some Quagsire on the foreshore begin firing rocks at them. Pikachu escapes from the Team Rocket’s clutches and Ash uses Bulbasaur’s razor leaf attack to free the other remaining Quagsire. Once free, one of the rocks punches the balloon and Team Rocket disappear into the night sky.
All of the Quagsire then grab their round objects and swim upstream to their home at the Blue Moon Falls. Upon arriving, each of them uses their water gun attack to fire their round objects at the moon. Brock observes that it is some kind of competition to see who gets theirs closer to the moon. The Quagsire with Ash’s GS ball fires his last and it appears to go the highest. The Quagsire are extremely happy and begin cheering, but Ash’s GS ball begins to float back downstream. Ash, Misty and Brock chase after it but it is not until the next morning that they catch up with it. After arriving at a location where a whole bunch of people appear to be gathering to collect their round things, our friends, although exhausted claim their GS ball and as it was the last one to come back down the river, Ash will have the best of luck this coming year.