A contrived but exciting adventure in which a summer vacation on the Connecticut coast becomes a hunt for sunken treasure. Impelled by a sudden enthusiasm, 11-year-old Tony invests all his savings in a small sailboat before leaving for his Portuguese grandma's and the small town of Swallows Bay. There, while taking sailing lessons and learning about the vagaries of weather firsthand, he discovers a mysterious couple in a motorboat, who seem to be searching for something. The town is associated with a vague shipwreck story; after uncovering some clues in an old ship model, Tony follows the couple into a foggy storm that leave him stranded on a small island. During a desperate swim, he sights the centuries-old wreck and is then rescued by the couple, who try to buy his silence concerning their illegal activities. Though very fond of money, Tony, without hesitation, opts to turn them in. Avi expertly captures the pleasures of small-boat sailing while building suspense and putting Tony in enough danger to keep the story moving. Lighter fare than The True Confessions of Charlotte Doyle (1990, Newbery Honor Book); still, fine, low-violence mystery.