Granny goes to extreme measures to keep Elly from Mark, who she's convinced is turning the family into frogs. Mark tells Jed more about his naval duties, especially about harvesting food from the sea.

Mark shows Granny and the rest of the family a film about his navy job to help her understand his frogman activities. She remains unconvinced. Mr. Drysdale is alarmed that Jed wants to invest millions in underwater farms.