S5E16 : Summer Love (a.k.a. Beach Story)

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.