A bit late, sorry, but a couple of thoughts
In section 63 of the judgement
"If Mr Moore were right it would be necessary to conduct frequent surveys of all inland waterways for which CRT is responsible in order to obtain up to date details of the position of the deepest channel and to record the same ..."
They should be doing this anyway in order to know where to carry out dredging, so it is not a problem.
In section 65
"it seems to me that it is not normal to assume that a pleasure boat will be "kept" in such a thorough fare at all"
I'm guessing, but in artificial channels such as lock cuts the main navigable channel will be the whole width, and it is quite possible to "keep" a boat there.