I saw two just like that Mike, on a swollen river, a woman middle aged and the man quite elderly, came paddle boarding pass me into a very deserted river further up. The banks were high and full of vegetation so if they came off, nowhere to climb up on the bank and no one to rescue them. There is a picture of them on the HDYGO thread somewhere, the lady was dressed in pink trousers, the river was up about 5ft up, brown and dirty with boils and swirls all over it, absolutely mad. So, I am not surprised someone has drowned somewhere, it was going to happen.
As to canoes and other water users, if the problem is bad enough to stop me fishing effectively I don't go there, I had two places like that on my club but fortunately they have two other stretches canoe free that I like and for £40, just about worth it.
I don't mind them, where I came across it, mostly they were quite cheery and polite, there were people enjoying themselves, and they have every right to do that. I don't care if they don't pay for it, just happy that some people get something for free in this life and I wouldn't want to be the one personally to end their enjoyment by evoking some ancient law of right of way.
What I do think is that anglers and paddle boarders etc., where there is an issue between them should agree times or days that one or the other can be done so both parties can do their hobby without clashing. This wouldn't be practical everywhere but I think a lot of cases it would be if an agreement could be reached, or is it too late now to have any sort of amicable talk with these people, is that anglers fault? Generally they do seem to think they should take precedence over anything or anyone else.