Peter Duck: A Treasure Hunt in the Caribbees (Swallows and Amazons 3)

Blurb

Peter Duck is the third book in the Swallows and Amazons series by Arthur Ransome. The Swallows and Amazons sail to Crab Island with Captain Flint and Peter Duck, an old sailor, to recover buried treasure. During the voyage the Wildcat is chased by another vessel, the Viper, whose piratical crew are also intending to recover the treasure.
The book, first published in 1932, is considered to be one of the metafictional books in the series, along with Missee Lee and perhaps Great Northern?.