I have been wandering along the C&O canal for many years and this is the first time I have seen the mules in action. We came upon the boat ride being offered by the National Park Service on the canal at Great Falls by chance.
The Charles F. Mercer, the boat used for the tour, is a replica of the original canal boats. It replaced the previous canal boat replica, The Canal Clipper III, which had fallen into a state of disrepair, in 2006. There is some nice information about the boat here.
Incidentally, it looks like excursion boats have been operating on the C&O Canal for a very long time. There is a document about excursion boats on the C&O canal that has been posted online at this location. This is the current version of the document. There are fascinating pictures in the document. The “Reminiscences about Mules” in Appendix B is very interesting.