For most people down a river means just that, away from the source and towards the sea -- hence downstream and upstream. You must have a different dictionary... 🙂
That's not the question you asked which replied to before you edited it though, is it?... 😉
The answer to your new question is -- none AFAIK, in fact it's very likely that it's never happened, because anyone doing this is going to be well aware of the risks and take far more care than yer average boater. If it's never happened then insurers are probably not going to worry about it -- at least, until it does... 🙂
Also most boats sunk by cillings are hire boats, where this would never be an issue for obvious reasons -- the longest boat you can hire up there is 57' and these go through the C&H locks just fine. Though I'm sure you could sink one in a lock if you tried, just like any length boat... 😉
Already done that, thanks -- Nigel was helpful as you'd expect. But have now largely gone off the crane idea for this short trip in favour of a boatmover -- or one of two, both recommended by more than one helpful CWDF poster, rather than my original choice... 🙂
Even from Cambridge, when it's clearly "down" on the map -- but that's because on trains all "up" lines lead to London, blame the Victorian railway companies for this.
I somehow doubt that the same applies to rivers like the Trent... 😉