Timmy is waiting at the bus stop one rainy Monday morning, and his cheap umbrella is doing no good to protect him from the rain. He tells Cosmo and Wanda that he wishes the rain would go away, but Wanda tells him that's a bad idea. He then wishes the "stupid water" wouldn't touch him, and Cosmo grants that wish before Wanda can object to that as well. Timmy arrives at school all dry, explaining to Chester and A.J. that he has really good water repellant when they ask why he's not wet.
Later that day, Timmy begins to see some negative effects of his wish. When he tries to drink some water from his thermos at lunch, it rushes out in a wave, missing his mouth and drenching Francis. Then, when he tries to get a drink from the water fountain, the water bends away from him, and Mr. Crocker sees this happening. Back in class, Timmy gets so thirsty that he tries to go drink from the class's aquarium, only to have half the water splash out of the tank as soon as he gets close to it, disrupting the class and catching Crocker's attention again. Cosmo and Wanda, in their fish forms, appear inside the aquarium, and Timmy tells them he has to unwish his wish. Wanda tries to tell him there's a catch to that, but she and Cosmo stop talking when Crocker walks over and notices the pair. Timmy, trying to hide Cosmo and Wanda's existence from him, answers that they're two new fish the principal donated. Later, as Timmy's gym class is out playing dodgeball (with Francis still upset about the incident earlier), Crocker, having figured out that the water avoiding Timmy is the work of fairy godparents, hatches an evil plan.
Later, Timmy is having trouble showering off from gym class, so Cosmo and Wanda magically clean him up and then explain the problem with him unwishing his rain-avoiding wish. Because Timmy has disturbed one of the four basic elements, Wanda explains, a big batch of water will come and drench him once he unwishes the wish. But before Timmy has a chance to wish the problem away, Mr. Crocker's voice comes over the loudspeaker, ordering Timmy to report to the school swimming pool. Crocker is there with a video camera, with which he intends to record proof of Cosmo and Wanda's existence, and then orders Timmy to jump in the pool, knowing that the water will avoid Timmy. But right there, Timmy wishes the water would touch him again. Immediately, a big batch of water floods in and drenches Timmy, also knocking Crocker away, soaking his camera and making him drop his glasses. Back at Timmy's house, Timmy and the Cosmas celebrate outsmarting Crocker again.