Ash's team members (minus Pikachu) for this episode
Ash and Pikachu's journey has led them to a rocky seashore. Ash lets out his team of Totodile, Corphish, Leavanny, and Rowlet to enjoy the scenery as well. Corphish gets especially excited at seeing the sea again and dashes into the water, knocking his teammates into the shallows in the process. Pikachu decides to try fishing with his tail, but soon regrets this as a Clauncher pinches down on his tail. As Pikachu pulls Clauncher out of the water, Corphish rushes back and challenges his fellow crustacean to a showdown of strength. While Ash scans Clauncher with his Rotom Phone, Corphish gets pushed back. Impressed by Clauncher's strength, Ash decides to catch it, but before he can throw his Poké Ball, a fishing line with a familiar lure attached to it wraps around his arm. Ash turns around to look and sees that the line was cast by none other than his old traveling companion, Misty, who declares that she will be the one to catch Clauncher. Clauncher, however, uses Water Gun on the ground to create a cloud of dust and escapes back into the water.
After greeting Pikachu, Misty congratulates Ash on becoming a World Champion, and reveals that seeing his battle with Leon had gotten her so fired up that she had decided to set off on a new journey herself, leaving the Cerulean Gym in her sisters' hands. She also explains that she's encountered this same Clauncher several times before and believes that fate has led them together. Ash, meanwhile, sees how competitive his Corphish has gotten with Clauncher, and wants to catch the Water Gun Pokémon for his sake. Misty declares they'll settle this with a fishing battle and whips out her rod. Ash agrees to this and responds in kind. Misty is baffled to see the lure Ash is using, which he reveals to be from another friend of his. She questions why he isn't using the lure she gave him, with Ash teasingly responding that this lure actually catches fish, unlike her lure, much to Misty's irritation.
The fishing battle begins, with the first one to reel Clauncher in getting the first chance at trying to catch it. Ash, as impatient as ever, quickly grows bored of waiting and starts complaining, irritating Misty again. Unnoticed by the two, Team Rocket is observing them from their Magikarp submarine, although they're too weak from hunger to actually do anything. When Misty finally gets a bite and reels Clauncher out of the water, Team Rocket's Rotom Phone tells the trio that Clauncher's big claw is full of delicious meat, and it grows back if broken off. Meanwhile, Clauncher manages to pull Misty into the water, causing Ash to laugh at her until he gets a bite as well. However, like Misty, he gets pulled back by Clauncher instead of the other way around and falls into the water as well.
Clauncher has a conversation with Corphish, and Ash eventually deduces that Clauncher wants him and Misty to battle in order to decide which of them gets to catch him, which Clauncher confirms with a nod. Misty happily accepts this, but before the battle can even start, Clauncher is caught in Team Rocket's own fishing line. The trio emerges from their submarine, reciting their motto, though their hunger makes them so weak that Misty can't make out what they're saying. The trio declares that they'll be using the meat inside Clauncher's claw to satisfy their hunger, much to Misty's distraught. However, this scheme ends up being short-lived, as Corphish cuts Clauncher loose, and the two Water types charge at the submarine together. Too weak to escape, Team Rocket is struck by a double Crabhammer and sent blasting off.
With the distraction settled, Ash and Misty prepare to begin their one-on-one battle. Misty chooses Politoed, and while Pikachu expects to be chosen, as Electric-type Pokémon are strong against Water types, Ash instead decides to use Corphish, much to Pikachu's shock. Nevertheless, he instead acts as the referee. Before starting, Corphish has another moment of connection with Clauncher, which again irritates Misty. Ash, however, is amused, writing it off as them having a moment between men. The battle finally starts, and Ash makes the first move with Crabhammer, but Politoed dodges it with Bounce, which also lands a hit on Corphish. Politoed next attacks with Focus Blast, but Corphish uses Metal Claw to suppress the move before charging in with a swift Aqua Jet. Misty has Politoed dodge it and counterattack with Hydro Pump, which Ash counters by ordering another Aqua Jet. Using Aqua Jet, Corphish maneuvers around the Hydro Pump and lands a hit, knocking Politoed to the ground. Ash orders a Crabhammer for the finish, and the move seemingly connects with a huge burst of dust. However, when the dust cloud clears, Politoed is revealed to have caught the attack before it could hit. With its opponent stuck at a close range, Politoed uses Mega Punch, which knocks Corphish out, thus making Misty the winner. While Ash comforts Corphish, who cries inconsolably after his loss, Misty claims her prize by catching Clauncher. She celebrates with Psyduck and Azurill for a moment before, to her surprise, Clauncher suddenly emerges from his Poké Ball and goes to train with Corphish. Ash and the rest of his team decide to join in on the training, too, while Misty is left frustrated at Clauncher having a deeper connection with someone other than the one who had just caught him. Above them, an invisible Latias appears and observes the scene.
At dusk, Ash and Pikachu continue their travels through a forest, though they both quickly notice Misty trying to secretly follow them, with Ash telling her to show herself. She expresses her desire to come with him, though she insists it's only so that Clauncher and Corphish can continue to hang out together. Ash pretends to be disinterested in the idea, but when Pikachu shows he wants Misty to come along, Ash accepts the request, officially reuniting the two old traveling companions once more.
The plot of this episode is similar to that of The Totodile Duel, where Ash and Mistyfish and battle over who gets to keep a Water-type Pokémon, only with Misty winning the Pokémon in question this time.
Additionally, the Pokémon they fought over, Totodile, appears in this episode, as well as the Pokémon Misty uses in their battle being the same.