Now I have read everything!
I remember a WDD (Wet Dinghy Drill) with some non-swimming Nigerian indigenes. Well, fitted with a life vest they were required to go in the deep end feet-first and then pull the toggles, when they would come bobbing up again. Sorted, sort of. I don't know exactly how much use they would have been to the pax but at least I wouldn't have been kept busy trying to keep my crew from drowning.
We did give very basic swimming lessons to the cabin attendants, so that they could at least dog-paddle. Isn't that good enough to qualify as "swimming," or is it so that people from South Africa are uniquely terrestrial and non-aquatic?