Ash and friends are continuing their journey to Nimbasa City. The group lets out all of their Pokémon, excluding Iris's Excadrill. Ash decides to take Trip's advice in the previous episode and help Oshawott perfect Aqua Jet.
Ash and Oshawott go to a nearby lake. They jump in the water and begin training. Ash tries to get Oshawott to open his eyes underwater, but he refuses. So Ash forcibly opens Oshawott's eyes. This scares Oshawott so much that he uses Water Gun on Ash, blasting him out of the lake. Ash, frustrated, decides to go back to the group with Oshawott.
Back at the camp, Cilan is cooking lunch while Iris watches. All of the Pokémon are having fun playing together, except for Snivy and Emolga, as they keep getting into fights. Ash's Scraggy wanders off and finds a group of Foongus. He begins to Headbutt them like he does with every other Pokémon he meets. However, the Foongus become angry and attack Scraggy with PoisonPowder. This makes the other Pokémon go and see what happenend, but when they get there, they get attacked by PoisonPowder as well! The Foongus run away as soon as Iris and Cilan come to see what happened. They are shocked. Soon Ash and Oshawott arrive and Iris tells Ash what happened.
Iris says she needs special herbs found at the bottom of lakes in order to cure the Pokémon. Iris volunteers to watch the Pokémon, while Ash, Oshawott, and Cilan go back to the lake. They arrive, and Oshawott goes to the bottom of the lake. The problem is, his eyes aren't open! So Oshawott swims right into an angry group of Tympole, who begin to attack him. Ash, watching from above, tells Oshawott to use Razor Shell, but since Oshawott has his eyes closed, he is just swinging his shell aimlessly. So the Tympole use a group Tackle to send Oshawott out of the lake. Cilan suggests that Ash himself should go claim the herbs, and Ash agrees.
Meanwhile, back at camp, the condition of the Pokémon is becoming worse. Iris becomes extremely worried and wonders how the boys are doing.
Ash swims down the the bottom of the lake, sees the herbs, and attempts to swim over and grab them. However, the Tympole are back! Ash swims back to the top of the lake for safety. Down at the bottom of the lake, a Palpitoad, the leader of the Tympole, teams up with his friend Stunfisk. They swim to the top of the lake and challenge Ash and Cilan to a battle. Cilan takes out his fishing rod, and says he will distract Stunfisk while Ash and Oshawott battle Palpitoad.
Oshawott and Palpitoad begin battling. Cilan also manages to hook Stunfisk! It starts flailing around, trying to get free, but to no avail. Oshawott tries to attack Palpitoad with Water Gun and Razor Shell attacks, but since Oshawott can't see underwater, it fails. Palpitoad counters with powerful Hydro Pump and Mud Shot attacks. Ash tells Oshawott that he can do it, so Oshawott manages to open his eyes during a powerful Aqua Jet attack, slam into his opponent and knocks it out. Ash throws a Poké Ball, and catches Palpitoad. Meanwhile, Stunfisk has made itself dizzy by flailing, and accidentaly flails onto land and Cilan catches it. Oshawott then goes down to the bottom of the lake and grab the herbs.
Back at camp, Ash, Oshawott, and Cilan arrive just in time. Iris makes some medicine for the Pokémon, and they immediately start feeling better! Ash tells Oshawott how proud he is for mastering Aqua Jet, and the other Pokémon cheer for him.
