I have recently been sent links to explorations of the Butterley Tunnel on the Cromford Canal, whose Friends are here with a map here and the first of the explorations here. The second exploration [don’t try this at home, kids] is described rather more extensively in this PDF.
Coincidentally, I found that Joseph Tatlow paid a brief visit to the canal in about 1869:
After about eighteen months of office work I had a long and serious illness and was away from duty for nearly half a year. The latter part of the time I spent in the Erewash Valley, at the house of an uncle who lived near Pye Bridge. I was then under eighteen, growing fast, and when convalescing the country life and country air did me lasting good. Though a colliery district the valley is not devoid of rural beauty; to me it was pelasant and attractive and I wandered about at will.
One day I had a curious experience. In my walk I came across the Cromford Canal where it enters a tunnel that burrows beneath coal mines. At the entrance to the tunnel a canal barge lay. The bargees asked would I like to go through with them? “How long is it?” said I, and “how long will it take?” “Not long,” said bargee, “come on!” “Right!” said I.
The tunnel just fitted the barge, scarcely an inch to spare; the roof was so low that a man lying on his back on a plank placed athwart the vessel, with his feet against the roof, propelled the boat along. This was the only means of transit and our progress was slow and dreary. It was a journey of Cimmerian darkness; along a stream fit for Charon’s boat. About halfway a halt was made for dinner, but I had none. Although I was cold and hungry the bargees’ hospitality did not include a share of their bread and cheese but they gave me a drink of their beer.
The tunnel is two miles long, and was drippingly wet. Several hours passed before we emerged, not into sunshine but into the open, under a clouded sky and heavy rain which had succeeded a bright forenoon. I was nearly five miles from my uncle’s house, lightly clad, hungry and tired. To my friends ever since I have not failed to recommend the passage of the Butterley tunnel as a desirable pleasure excursion.
Joseph Tatlow Fifty Years of Railway Life in England, Scotland and Ireland The Railway Gazette, London 1920