Brock made the lunch and May and Max set the table. Ash sees his five Hoenn badges, ready to get three more. Max asks him to bring some water, but while Ash goes, he stumbles upon a can - his badge case flies and is devoured by a huge Water Pokémon. The Pokémon - Whiscash - dives into the water. Ash demands his case and Whiscash shows the case (on its tongue), but taunts him by taking the case back and going into the water. Ash is angry and sends Corphish and it uses Crabhammer, but is soon defeated by Whiscash's Water Pulse. Whiscash goes back to water, so Ash has no choice to get in the water.
Whiscash goes among some weed and Ash follows, but soon finds to be tied by the weed. Ash struggles to free himself, but runs out of air. He sees Pikachu and gets him, but soon gets on a boat with a man, saving himself. The fisher is amused when Ash catches Nero (the Whiscash) with his own hands. The fisherman tells that Nero claimed the lake as its own. Whiscash must have gotten the case when it sparkled. Ash gets upset having lost his badges, but the man (introducing himself as Sullivan) will get the badges back. Max wonders if he calls himself the fishing God, being the master of fishing, why didn't he catch the Whiscash, so Sullivan is depressed, leaving them. However, he comes back when they convince him they need him.
Sullivan gives Ash some rods, so he does not give to Brock, May and Max. When they mention he's the fishing God, he gives him the other rods. The gang chooses the fishing lures - Ash Pikachu, Brock Lotad, May Psyduck, Max Kecleon and Sullivan a Butterfree lure. Sullivan made a plan to get that Whiscash, while Team Rocket overhears and observe the situation. Meowth doubts that they'll get a Whiscash, but his doubt is soon removed when he sees a one and makes an idea - they'll give it to their boss.
The gang catches nothing, while Sullivan caught a Carvanha, Magikarp and a Remoraid, but frees them back. The gang arrives to Sullivan to give them advice, so he does (after they call him the legend). He shows them some spots where they could capture Water Pokémon. Sullivan throws the lure between the trees. Ash goes to throw on the same spot, but he fails, so Sullivan says that he should practice before aiming correctly. Max throws his lure and the lure is in the spot he wanted, amazing everyone but Sullivan who practices a long time. Max soon gets something - it is Whiscash, but a small one than Nero. Nero appears soon after, showing the badge case and disappearing.
Team Rocket fishes, but with no result. James is frustrated when he borrowed Jessie a bottle-cap as a lure, but Jessie is soon attacked by a Feebas. She gets it off her hair. Ash and May did not get any result either, so Sullivan gives them advice to move to a different spot. Jessie is attacked again by a Feebas, so she gets it off again. Mewoth proposes to use Jessie's hair as bait for Whiscash, but she denies it. James spots the gang fishing, so they plan to steal Whiscash after they capture it. Ash remembers his badges and people he fought to get them, so he promises to get them back. Sullivan concentrates, and throws his lure, knowing that Nero is nearby.
Sullivan gets the Pokémon, but it is a Magikarp. Ash gets something, so Sullivan says he should pull in opposite direction. The Pokémon is Nero, but Nero pulls the boat, throwing Ash off balance. Ash sends Corphish and orders it to use Crabhammer on him. Corphish thinks for a while, but does it, so Ash is sent to the rocks. Ash pulls the Whiscash, throwing him on the shore. Ash sends Grovyle and he uses Pound, hurting it badly. Whiscash taunts Ash, but soon Team Rocket captures it. They fly off using rockets, so the gang uses the boat. Brock sends Lombre and Mudkip, using Water Gun to speed the boat up. Grovyle uses Bullet Seed, blowing the baloon. The gang arrives while James sends Cacnea, ordering it to use Pin Missile.
Grovyle uses Bullet Seed, damaging Cacnea. Jessie sends Seviper and it uses Poison Tail, but Pikachu counter-attacks with Iron Tail instead. Meowth is about to capture Pikachu, but Whiscash frees itself, jumping and shaking the ground. Pikachu uses Thunder, blasting Team Rocket away. Whiscash coughs, releasing the case to ash. Nero is about to get back, but Sullivan wants to battle it, sending Flaaffy. Hannah (the Flaaffy) uses Dynamic Punch, hurting Nero. Nero uses Water Gun, but Hannah dodges and attacks with Iron Tail. Hannah attacks Nero with Thundershock, but Nero seems unhurt. Max wonders how come Sullivan did not get a plan, so he remembers something...
He gets a Master Ball out and goes to capture Nero, but Nero devours the Ball and goes back into the lake. Sullivan decides to still get Nero. The gang leaves Sullivan, leaving him to get Nero.
- Featured Pokémon: Vigoroth, Slackoth, Machop, Zangoose
- In the beginning of the episode, a classic Pokémon identification can be see. In this case, it is a Krabby.
- This is the first and, so far, only time where the Master Ball has been used in the anime.
- Whiscash swallows Sullivan's Master Ball, and is not captured. However, in Berry, Berry Interesting!, a wild Munchlax swallows a Poké Ball and is captured from the inside out.
- Ironically, Master Ball should capture Whiscash, no matter what.
- This is the second time the main characters are seen fishing in Hoenn. Oddly, Sullivan has to teach Ash and company to fish, even though Ash and Brock have fished several times before and all present protagonists fished in Gone Corphishin'.
- This would be the last time the move Earthquake was used in the anime. The move itself would later cause an episode to be banned because of a real earthquake. Earthquake has not been used or seen since.
- The Poké Ball outline on Ash's Badge case is changed to a rectangle in the dub once again.