I’m unreliably informed that the absolute minimum amount of liquid to drown a human is 1 liter. That might require a special head-shaped bucket, but it seems plausible.
But out of curiosity, what sort of statistics are you seeing about UK people falling into canals? I know they have canals and people, but I thought the trope was shopping trolleys (USA: shopping carts) falling into canals. Is this a serious issue? Can we find comparable figures from the canal-strewn Netherlands for comparison?





There might exist one, but it probably doesn’t haven’t much volume or isn’t well federated because few other instance want to interact with spammy, problematic, high-complaint instances.
What you’re describing might be a Level Three in the moderation speedrun: https://www.techdirt.com/2022/11/02/hey-elon-let-me-help-you-speed-run-the-content-moderation-learning-curve/