As Team Rocket is on a beach, James expresses how relieved he is that they have made it back to shore and Meowth remarks that they can now think of a way to steal Pikachu again. Jessie, however, just wants to relax. James and Meowth turn to see her lying on a lounge chair in the shade of a beach umbrella. They begin to complain, but she ignores them long enough to enjoy a brief sip of her tropical beverage before explaining that she just wants to take it easy today. The three continue to bicker until James and Meowth notice that Wobbuffet is stretched out on another chair. This sends the two over the edge, and the tension escalates as they yell at the Pokémon. While they fight, a strange creature speeds towards the beach from the ocean. Jessie notices it and screams. The mysterious creature rams them from under the sand, sending the group flying. The creature then burrows into the ground off-screen.
Meanwhile, Ash and his friends are camping on a nearby stretch of beach. Ash declares that there will be a lot of training today to prepare them for the rematch with Brawly. As Lotad waddles up with some water, he and Pikachu begin to wash their faces. May and Max sit at a nearby table brushing their teeth while Brock and Torchic start a fire to prepare a stew. Ash releases his Taillow and Treecko, and they--along with Pikachu--begin to meditate on the shoreline. Ash starts to explain to his Pokémon the importance of meditating, and for them to think about winning their upcoming rematch. May wonders what he is doing as Max sits at the edge of a pool of water washing clothes. Forretress then collects and dries them with its Rapid Spin attack. Max thanks it and brings the clothes to May for her to hang up. May asks Max why Ash is spending all his time meditating and Brock informs her that meditating is actually a form of training, as it prepares Ash and his Pokémon for their battles. He also explains that such training is particularly important for Ash, as it teaches him patience.
A large wave approaches the shore. Taillow begins to freak out but Ash tells it to keep meditating, because if it can learn how to sense the waves, they may be able to beat Brawly and his surfing techniques. Taillow shuts its eyes and continues to meditate as Ash listens intently. The wave grows larger and nearer and Ash tells them all to get out of the way. They all get up and rush off, but when the waves recede, Pikachu is lying on the ground covered in seaweed. Ash checks on his Pokémon, now aware that they did not make it out in time. May and Max complain about Ash's training and that they're stuck doing all the laundry. Brock tells them that training isn't always about Pokémon.
Ash hangs up his wet clothes as he and his Pokémon try again. Ash orders them to run and this time, they all get away, but Treecko stays. It starts to open its eyes, but the wave hits it. Ash wonders why it did not move, and May and Max say that it must have waited a little too long, and that threw off its timing. When May tells Ash that Pokémon training isn't as easy as he thought it will be but practice makes perfect, Ash scolds May for not practicing her Pokémon coordinating. As Brock brings the group some tea, May leaps up and says she has been practicing her entrance. She then spins around and sends out Torchic and Wurmple. The two begin to play around, but May comments that they have to learn to be more graceful, and she begins to dance again. Max then comments that Coordinators can't let out two Pokémon at the same time in Pokémon Contests, and Brock adds it will not be a good idea for May to dance around like that, since in Pokémon Contests the focus is always placed on the Pokémon.
Suddenly, they all notice that the tent is walking away. The group gives chase and Ash orders Pikachu to shock it, but Brock stops him and explains that an Electric attack might set the tent ablaze. May tells Wurmple to stop it with String Shot, and it snags the tent. May then tells it to reel it in, but Wurmple seems to be having trouble. Treecko grabs on to help, but it is pulled forward. Ash and the others all grab the string and start to pull, but the creature under the tent causes them to trip. It drags them along the beach for a few minutes, and then retreats to the water, causing everyone to fall in. Once everyone's clothes are hung up to dry, Ash stands on the beach covered in sand. They inspect the damaged tent and the rice balls that litter the beach and wonder what could have done such a thing. Ash suggests that a group of Diglett did it, Brock thinks it was a Krabby and Max thinks it was an Aron. Brock begins to sew the tent up while exclaiming that a Pokémon that could pull all of them like that must be really strong, but May just thinks it was scary. Ash then becomes intrigued and decides he wants to catch it. Brock and Max agree to help, but May just sighs.
Meanwhile, up on a cliff, Team Rocket is recovering from their earlier blastoff. Jessie remarks about how strong that thing was while James and Meowth wonder what is was. Wobbuffet pops out at the edge of the cliff and Jessie turns and recalls it in exasperation. She then notices the mysterious creature speeding up the beach under the sand. She points it out to Meowth and James as the creature smashes into a rock and diverts direction. Jessie instantly wants to get it and begins to rush off, but lands on a sleeping Loudred. Jessie steps back and freaks out as the Pokémon angrily wakes up. It lets out a cry which sends Team Rocket sky high. That night, Ash and friends sit by some bushes and wait for the mysterious creature to reappear. May complains that she is tired and wants to go to bed, but Ash refuses to sleep. Max angers May with a smart-mouthed comment and she begins to tackle him. Pikachu then hears something and Ash asks if the creature is close. It signals that it is and they all freeze to look out at the Pokémon food they placed at the edge of the beach.
As they wait, Ash suddenly hears something behind him, but it is too late. The creature smashes into them, sending them all flying onto the beach. It continues its pursuit, prompting the group to split up. It decides to chase May as she runs screaming for her life. Ash turns around and tells Pikachu to shock it, and it does. The creature sinks into the sand, leaving a hole that they proceed to examine. Ash asks Pikachu if it can still sense anything, but Pikachu signals that it is gone. The following morning, the group is slumped against the tent in exhaustion. May comments that they should not waste their time catching it, but Ash gets angry. She asks him why he wants to catch something that almost killed her, but he still does not listen. Brock suggests they try a different plan and Ash says if it attacks again, he will tell Pikachu to shock it. He then adds that he saw a red "horn" protrude from the sand when it was hit by Pikachu's earlier attack. The group then heads back to the beach and Brock has Forretress make a huge hole in the sand with Rapid Spin. Brock thanks it and tells it to make more as Ash explains they are going to use the pitfall trick. May and Max cover the holes with leaves as Ash explains that when the Pokémon tries to chase them, it will fall into the holes. May and Max proceed to say that his plan will not work.
That night, the group waits in the bushes again while watching the Pokémon food. Ash notices three large bunches of seaweed emerge from the water. They walk up and begin to eat the Pokémon food. Brock says the plan is working and he sets some more food on a nearby rock. One of the seaweed bunches spies this and the three head towards the new food, only to fall into a hole! The group approaches, only to find that they have snagged Team Rocket. They begin to say their motto, but May and Max interrupt, asking why they were covered and seaweed and eating Pokémon food. Team Rocket cowers in the hole, saying they had to make do. Suddenly, the creature emerges from the hole and smashes into Team Rocket, sending them blasting off again! The creature slides up the side of the hole and heads towards the food, but Pikachu uses Quick Attack, sending it flying out of the sand. It lands with a thud and is revealed to be a Corphish.
Ash scans it with the Pokédex and Brock says that Ash should catch it fast, as its speed and power will be perfect in a match against Brawly. Ash agrees and sends in Pikachu as Corphish gets up. Max thinks the battle will be easy for Ash, as Corphish is at a disadvantage due to its Water type. Pikachu starts with Thunderbolt, but Corphish dodges and uses Bubble Beam. It then digs under the sand, leaving Pikachu confused. It looks around, but Corphish smashes up, sending Pikachu flying. As he falls, Pikachu tries to use Iron Tail, but Corphish catches him with its pincers and chucks him at Ash. Brock comments that this Corphish is stronger than he thought, and that Ash has a challenge on his hands. Ash agrees and lays all his trust in Treecko. Ash releases it and the match begins. Ash tells Treecko to meditate, and it closes its eyes and stands there. May wonders what he is doing but Ash seems to have a plan. The sun begins to rise and Corphish becomes impatient. It uses Bubble Beam, but Ash tells Treecko to hit them away. It uses Pound to break through the attack. Corphish begins to steam and rushes in for a Crabhammer, but Treecko uses Quick Attack, sending the Corphish flying. Then Treecko hits it with Pound and Corphish lands on the ground and Ash throws a Poké Ball, catching it.
Brock, May, and Max congratulate Ash for the capture and Ash releases Corphish. He kneels down and introduces himself, saying he hopes to train it well. Corphish smiles and shakes his hand, but ends up tossing Ash in the process. Everyone laughs and the scene ends with Ash celebrating and his new Pokémon.