The Scarecrow of Oz (Oz Series, Book 9)

The Scarecrow of Oz is the ninth book in the Oz series written by L. Frank Baum. Published on July 16, 1915, it was Baum's personal favorite of the Oz books and tells of Cap'n Bill and Trot journeying to Oz and, with the help of the Scarecrow, overthrowing the corrupt King Krewl of Jinxland. Cap'n Bill and Trot (Mayre Griffiths) had previously appeared in two other novels by Baum, The Sea Fairies (1911) and Sky Island (1912).
Cap'n Bill, a sailor with a wooden peg-leg, and his friend, a little girl named Trot, set out from California on a calm day for a short ride in their row-boat. A freak whirlpool capsizes their boat and pulls them under water, where they are carried by mermaids (referred to but not seen) to a cave. They are soon joined by a flying creature called an Ork. Passing through a dark tunnel out of the cave, the three arrive at an island inhabited by a grim man calling himself Pessim the Observer. Cap'n Bill and Trot reduce their size by eating magic shrinking-berries, and the Ork carries them away from the island to the land of Mo, where they eat another type of magic berries and resume their normal size.