How about singing when on the canal? A couple of friends pointed out that singing is a good way to pass the time in a tunnel, and the acoustics are great. We tried it in Foulridge tunnel, Leeds and Liverpool canal, famous for the swimming cow.

Took about 20 minutes to get through so we got through several songs. At the other end, my wife asked the people in the boat following us if they'd enjoyed the singing - the reply was "... we thought you had your head stuck"!