Secret Water is the eighth book in Arthur Ransome's Swallows and Amazons series of children's books. It was published in 1939. This book is set in late August or early September 1932, towards the end of the summer holidays (immediately following We Didn't Mean To Go To Sea and located in and around Hamford Water in Essex, close to the resort town of Walton-on-the-Naze. It brings the Swallows and the Amazons together and introduces a new group of characters, the Eels.