Seven-year-old Emily, a petite child with stentorian pipes, takes ship with whispery Captain Baroo and his ""kind but luckless"" crew rather than enroll in Miss Meekmeister's School for Soft-Spoken Girls. Soon she's indispensable, bellowing orders into the gale 'AVAST! LUFF HER UP BEFORE WE'RE STOVE!' ""--and summoning up friendly whales to steer the ship away from rocks. Ultimately, she finds an even worthier use for her talent, as a human foghorn for her New England hometown. Evoking American Primitive conventions, Carpenter poses stiff, comic wincing figures, clad in early 19th-century dress, in carefully appointed interiors and bustling outdoor scenes. An appealing nautical tale, this will have reflective readers wondering why whales would come to the rescue of a whaling ship, but O'Neill's language has a roll and verve that captures her young heroine's spirit perfectly.