I'm visualising the drownee tragically encountering a grammar pedant as he thrashes about:
Drownee: "I will drown! I will drown!"
Grammar pedant: "Oh. I was going to help, but if you're determined to die I'll leave you alone to get on with it."
maximus otter
An amusing scenario — except for the drownee — but only if it is the sort of grammar pedant who parrots a rule they once heard and accepted at face value, without looking into it more deeply, or considering how they hear the language used on a daily basis.
Here is one source among many.
https://blog.oxforddictionaries.com/2013/09/25/will-versus-shall/
The "will = intention, shall = despair" interpretation comes from the fact that "will" has more than one meaning. It's a bit like the less/fewer thing: the more you look into it, the more you realise that it is an arbitrary attempt to impose a rule on language that is naturally used in a more flexible way.
"Will" derives from an old word meaning "wish". "Shall" derives from an old word meaning "owe". Meanings and usage change in the normal course of the development of language, and "shall" is declining as "will" is in the ascendancy.
That aside, this thread is interesting, and an object lesson for Fortean discussion. The initial idea was that a large number of unidentified bodies found in the canals may point to a serial killer. This was followed by careful analysis of population densities and demographics. Individual cases were cited for comparison. Several competing explanations have been considered rationally. I enjoyed reading it.
To my mind, the fact that most of the bodies were unidentified suggested immediately they were not part of the mainstream settled community. That immediately suggested homeless people, many (but certainly not all) of whom are vulnerable through having suffered abuse, mental health issues, alcohol or drug abuse. A combination of misadventure, unrelated isolated murders or manslaughter, and suicide is the likely explanation. In order to hypothesise a serial killer, you would need more of a pattern than "they were all found in the canal".