Handsome surfer Duke Williams rides a giant tsunami to the island. At first, the castaways are excited as Duke thinks he will turn around and surf back to Hawaii (and send help). However, after seeing Mary Ann and Ginger, he decides he may want to stay for a while. The castaways must come up with a plan to make him want to leave for Hawaii.

An loin-cloth clad ape-man (Tongo) comes to the island, and makes off with their food and supplies. Actually, he is an out of work actor, who tries to convince the Castaways that he is a real uncivilized ape-man while studying for an upcoming role. After he cowers when confronted by a ""real"" gorilla, he leaves the island and the Castaways behind.