This is slightly tongue in cheek, but also...not really.
I can't swim, so can imagine wearing one of those less bulky life vests with the gas canister most of the time. I know, right "can't swim and contemplating a boating life"? I hear you. Trouble is, it's more than just learning the physical act, it's claustrophobia of immersion.
Anyway, to that question...how often DO people fall in? No matter how careful you are? I'm talking about liveaboards. Would you say it was a case of "when" rather than "if'? In other words, even if you are really careful, the day will come when you slip on a wet surface, stumble on the roof, lose your balance while dealing with the boat in a lock, etc?
Or are there those among you here who can say, hand on heart, the likes of "I cruised the canals for six years and never fell in once"?
Is it like they say for motorcycles? You're not a real boater until you fall in (off)?
Canal water is not something I would want to fall into in general, let alone for the drowning aspect.