Corpse size has a lot to do with it. I wouldn't swim in even a large pool with a dead human in it (knowingly), but one dead fish or rodent or dozens of dead tadpoles or bugs? Not an issue.
Heck, most household swimming pools have dozens of dead bodies in them, but they're 99% insects.
The whole premise of this meme is a bit silly. If there was a corpse floating near the beach, I think most people might wait for the corpse to be removed, and perhaps even a reasonable cause of death to be determined, before entering the local area. The same is true for pools.
If you knew there was a dead person next door you might be a little uncomfortable, but could go about your day. If you knew there were 50 dead people next door you would need to get out of there.
The number is relevant, not just the proximity to the closest one.
Nobody panics when things go "according to plan." Even if the plan is horrifying! If, tomorrow, I tell you that, like, you'll walk through a graveyard, or a morgue, nobody panics, because it's all "part of the plan". But when I bring ONE corpse to a job interview, well then everyone loses their minds!
People are often uncomfortable in graveyards and, for example, would not want to walk through one at night when they would be willing to walk through a field.
The dirt does provide a sort of insulation however, as people would be more willing to walk through a graveyard than through a house that had the same density of corpses in the basement. It's the theoretical accessibility to the corpse that plays a factor here.
Similar to the water:piss ratio regarding (US?) swimming pools, insofar as the knowledge that the "nostalgic" smell of swimming pools is not the comforting presence of chlorine so many believe it to be, and is in fact the confirmation of a volume of piss in the water that is rapidly nearing the extent of said chlorine's capacity to neutralize (sapped also by ceaseless sunshine & innumerable contaminants hitching rides on patrons' oblivious meatsacs).
In short: if you smell "pool", someone(s) have pissed in it. A lot.