if you have a look at this waterways map:
http://www.waterexplorer.co.uk/gmaps...ecanalmap.aspx
and find Sheffield and then look across to the left you will see New Mills (just under Glossop), Stockport a bit further left and Macclesfield a bit further south. The bit of canal between those last few places is the Peak Forest Canal and Sheffield is where he was going with it - as you see there's a vast blank bit in between where all those locks and tunnels might have been!
I agree about walking the narrow boats - can't say I'd fancy that much in the pitch dark with water and goodness knows what else dropping on you!!