If I were hiring a boat for a week or two I wouldn't need this extensive and invaluable map of the whole of the GB waterway system. If I had a boat for any longer, planning a route to maximise what you see is essential - this map fulfils that purpose.
Importantly, it tells you the size of boat each waterway/canal will take in both length and beam, plus any other key information you may need to know. Distances between points are shown in miles plus the number of locks there are in that stretch of the water - essential information for estimating time.
Whether you're really interested in the waterways of Great Britain, or intend to travel around the system, you'll be glad you bought this map.