After Ash's victory at Canalave Gym, they are about to go on a boat to Chocovine Town. However, there are no boats scheduled today. They ask a man who points at sea; a group of Wailord block the path. Dawn asks Ash what to do, but he thinks some lunch should be first. As they are about to have lunch, a Luxio snatches some food. Piplup goes to attack, but gets shocked by Luxio's attack. Luxio drops the food, but a Whismur gets it and runs away, causing Ash to chase it, but gets knocked out by a Nidoran♂. They taunt them and go away, so Pikachu and Piplup go to get them.
Team Rocket is working on a street. The Whismur, Luxio and Nidoran♂ go into the sewer. When Team Rocket spots the heroes, they activate the machine and go get Pikachu. Ash gets him and rolls into the sewer, where the machine cannot attack. With Piplup's Whirlpool, Team Rocket is blasted off. Dawn and Brock go to the manhole and Piplup tries to open it, but fails. The manhole is bent it won't open, so Ash goes to find another way out. Seeing the sewer is quite large, Ash sends Buizel to find a way out. As Ash goes, he and Pikachu spot the thieves. Luxio attacks them, so Buizel uses Aqua Jet to stop it, but it is quite strong. The Nidoran♂ uses Poison Sting and when the smoke clears, the thieves are not present.
When Ash goes further, he hears something. He, Pikachu and Buizel see the thieves are actually feeing a Wailmer, who is stranded in the sewer. Though a bit hostile at first, the Pokémon help Ash, Buizel and Pikachu push Wailmer to the water. When Ash scans Wailmer via the Pokédex, he learns that Wailmer becomes dry, so Buizel uses Water Gun to refresh it. The Wailmer becomes stable and goes into the water. Ash suspects it must be missing the Wailord in the harbor, so they all go. Happiny tries to get the manhole open, but it still won't open. Dawn sends Mamoswine to open the manhole, but it ignores her. Dawn offers her Poffins if it does that. Mamoswine happily does that, shaking the ground and opening the manhole. Mamoswine charges, sending Piplup and Dawn in the air. Still, Happiny gets them and Mamoswine its reward.
Ash and the Pokémon enter a chamber filled with many other Pokémon, which means Luxio is helping them. Dawn Brock and Piplup got into the sewer and yell for Ash. Piplup seems to know the way and goes somewhere, but Dawn has a feeling that it may not be the correct way. Ash has been led to a small sewage waterfall, where the Wailmer fell. Wailmer got a rope in the mouth and while Buizel pushes it from underneath, Ash and the Pokémon try to pull it up. With a lot of effort, they manage to get Wailmer up. But a higher waterfall exists and while Ash has doubts, he still promises to get Wailmer up and asks Luxio that if its friends may help them. While they go, Dawn, Brock and Piplup got somewhere, so Dawn is angry at Piplup for leading them nowhere.
The Pokémon agree to help Wailmer get up, so Ash explains the plan. When the Spheal freeze the water, they would make a slide and with some furniture, they would make a sledge. After Buizel and Spheal push the Wailmer, it would ride on the sledge and with Pikachu and Luxio's Iron Tail hitting the sledge, it should have enough power to get up. They make the slide and shape it, then they craft the sledge. Buizel and the Spheal push the sledge and get Wailmer on the slide. Pikachu and Luxio use Iron Tail and power it and while it may seem a success, the slide breaks because oft oo much weight. Still, Luxio uses another Iron Tail and a Venonat jumps into the Wailmer. The Wailmer is up and safe. As they are on the end of the tunnel, they meet up with Brock, Dawn and Piplup, who proved that he lead them to the right tunnel.
They are being told what happened. Luxio shocks Ash a bit to warn him of something. A Swampert emerges, using Mudshot to attack them, as they are on its territory. It attacks again, so Ash decides that Pikachu should use Thunderbolt, but Brock reminds him Swampert is a Ground type Pokémon. Ash sends Grotle, who gets hit by Swampert. Still, Grotle defeats the Swampert with Razor Leaf. They go out and just then, the Wailmer evolves into a Wailord. Because of the size, it cannot pass under the bridge, but Brock knows it is a drawbridge. Since they have no key, Pikachu uses Thunderbolt to power the machines, but it is not much. Swampert is coming back.
Ash falls down and tries to stop Swampert, but it is not listening. With Pikachu, Luxio and Pachirisu powering the machines, the drawbridge is rising, but still not enough. Luxio calls for help, as the Nidoran♂ and Rattata come and power the machine as well. With so much power, the drawbridge rises and Wailord passes underneath and the wave it leaves behind causes Swampert to be enulfed and leave the area. The Wailord rejoins its friends and they spray water to make a rainbow for such help. Ash tells Luxio it won't forget its help and gets shocked a bit, a way to thank him. Before they go to the boat, Ash is hungry and go to the Pokémon Center.
- Music from Lucario and the Mystery of Mew and Pikachu and Pichu are used as background music.
- Professor Oak's Pokémon lecture: Finneon
- The delay of ships by certain whale Pokémon is similar to the events that happen in Lilycove City in the games.
- A minor reference to the events of The Rise of Darkrai occurs during this episode, as Ash recognizes Luxio on sight despite his only encounter with one occurring in Alamos Town.
- This episode, which focused on saving a whale Pokémon, premiered on the same weekend that the Whale Wars first episode of the second season first aired.
- The way Team Rocket's mecha in this episode appeared is similar to how the Transformers appear.
- Team Rocket doesn't recite their motto in this episode.
- When the Rattata and Nidoran♂ are cheering after Wailord swims through the opened draw bridge, one can hear Pikachu talking. However, Pikachu's mouth, as well as the rest of his body, does not move.
- Nidoran♂ uses Bite alongside Nidoran♀ despite being unable to legally learn the move.
- When Ash stops Pikachu from attacking Swampert and brings out a Poké Ball, Pikachu can still be heard in the background attacking.
In the first airing of the episode, the end credits were shown twice.