Aquaticism - S7-E14
Trivia: In the opening intro the store next to Bob's is called "Pro-pain Accessories" and the exterminator is "Dale's Dead-Bug." Hank Hill, from the show "King of the Hill", sells propane and propane accessories and his neighbor, Dale Gribble, owns Dale's Dead-Bug. Jim Dauterive, one of the show's creator/writer was also a writer/producer for "King of the Hill."
Answer: S04e15, "The Kids Rob a Train."
Bishop73