Convoys per month does not show up on canals, neither does the freight overlay work on canal ways. Is this a bug?
Hmm - that is very curious. The code for adding this statistic is entirely missing for waterways of all sorts, and I cannot find the place where it should be added (it does not even appear in Standard).
Edit: On further testing, this seems to be reproducible in Standard. Moving thread accordingly.
Indeed, the relevant code parts are missing for ships...
Should be fixed with r7030.
Splendid! Now backported into the 11.x branch of Experimental, too.