I go boating on Loch Ness and the Caledonian Canal as often as I can.
I am a boaty person, and regard time spent walking about when you've a boat to go to as lost time, so I am used to using the folding map provided with the boat (from Caley Cruisers, Inverness), together with Admiralty Chart 1791. These concentrate mostly on the topography of the watery part of the landscape.
Non-boaty people aboard usually have OS maps of the area, which concentrate mostly on the topography of the solid part of the landscape.
This map/guide nicely brings together the two 'sides'; has enough shore-side detail for boaters and boat-walkers to plan drop-offs and walks and pick-ups; and good detail to read about the area.