How small are the pools where people don't expect to share lanes? The largest pool at the place I go to has maybe ten lanes and I'm trying to imagine the riot that would ensue if people were told that they had to wait for their turn. There's another pool there that's used for swimming laps but it has even less lanes and the place has something like a thousand visitors a day (though not everyone swims laps, of course). Fortunately the large pool is 50 m long and the lanes are wide enough that passing isn't a problem. I go there every week and I haven't seen any problems.
Where does Carrotte live?
This one was in Paris, so big capital (well the city does have a good 15 or so pools). A bit on the small side, 2 lanes for lap swimmers and 2 were open for the kids. There was at least 6 to 8 swimmers per lane at all time (I left because it got too crowded with 11 people in a 25m lane), and it was 4pm ( a slow time-slot then, I've been there at 11am/1pm and it's even more crowded.).
When I'm in a near suburb there's always 10 to 12 people per lane ( 4 lanes for lap swimmers, plus 2 'open' for the others)
There was no way you could spend more than 5 minutes and not realise that you share lane (or you would have done the smart thing like another poster said and ask someone). I think the weirdest thing is that he never looked afraid, or anxious, apprehensive of the water. Didn't seem to gather up courage.. He just looked like someone who would sit on a bench in a parc because he's 10 minutes early.
Maybe it's just that for me, going to the trouble of going to the pool, putting on a suit and all is boggling. (me, lazy? noooo..)
But who knows, I don't read minds and cannot say what he was thinking, just an odd occurence in my day I guess.