Grandpa Phil and his old friend have been feuding for quite some time, as their friendship fell apart years ago. However, they still attempt to compete with one another as they each believe they are the better individual; though when both men decide to enter the extremely dangerous Old Iron Man triathlon, Arnold attempts to put an end to their feud, as he does not believe they should risk their lives over something so trivial.
When Arnold, the boarders and the Patakis go to the beach, a girl uses Arnold to win a sandcastle competition. Ernie gets buried in the sand. Miriam and Suzie start taking dancing lessons. Grandpa thinks he's stuck on an island. Oscar starts using a metal detector to find ""treasure."" Big Bob gets a bad sunburn. Helga tries to warn Arnold that he's just being used.
When Mr. Simmons is upset that Principal Wartz is being too strict with the students, Wartz decides to resign and he selects Mr. Simmons to take his place. The newly promoted Principal Simmons decides to make massive reforms to permit the school environment to be more liberal, though will the students at P.S. 118 appreciate his authority?