This is book number 8 in the Godine Storyteller series.
Arthur Ransome's Swallows and Amazons series has stood the test of time. Ransome is not only a great storyteller, writing from first-hand experience, but each story celebrates eternally valuable qualities of practical knowledge, independence, and initiative. The twelve books are for children or grownups--anyone captivated by a world of sailing, adventure, and imagination.
In the eighth book in the series, the five Walker children are left on a "desert island" by their parents with provisions for a long stay and a blank map to fill in. Like all of Ransome's books, this is at once a real adventure and a lesson in the practicalities of exploring--in this case, of surveying the inlets, coves, mudflats, and estuaries of "Walker Island." Naturally, there are enemies to overcome (another clan named The Eels) and friends to meet (who else but the intrepid Amazons?).