In Captain Salt in Oz, the jovial King Ato of Octagon Isle and his Read Bird, Roger, eagerly join the former pirate, now Sir Samuel Salt, Royal Discoverer of Oz, aboard his magically enhanced ship, the Crescent Moon, for a voyage of exploration. Their adventures begin with claiming a volcanic island (Salamander Island, after Samuel collects a fire lizard) and navigating Patrippany Island, where they rescue Tandy, the young, haughty King of Ozamaland, from a jungle cage where he was being cared for by Nikobo, a talking hippopotamus. Nikobo and Tandy join the expedition, and Tandy gradually sheds his royal stiffness, becoming a valued cabin boy and artist. The crew encounters numerous wonders and perils, including a City of Bridges on Peakenspire Island, a dense Sea Forest, and a terrifying attack by a giant Narwhal (Sea Unicorn) whose horn impales the ship, only to be defeated by Tandy's quick thinking with a magic creeping vine. After being collected by jellyfish-like Seeweegians in a sea-hole and surviving a violent storm, they finally reach Ozamaland. There, they discover the treacherous Ozamandarins plotted to usurp Tandy, but with the help of Ato's magic plants and the unexpected intervention of Boglodore (the magician who initially abducted Tandy via a flying "umbrellaphant"), the villains are overthrown. Tandy, choosing adventure over immediate rule, appoints a regent and joyfully rejoins the Crescent Moon to continue exploring. This book is a rollicking sea adventure emphasizing discovery, friendship, courage, and the humorous clashes of different personalities and customs.