We never had them when I was a kid. There was “Adult Swim” but that was like a 3 hour block of time on a week night, legitimately so that adults could swim without being terrorized by cannonballs, marco polos, jacknifes, watermelons, palm geysers and the dreaded depth charge.
(There’s another recent development in swimming pool administration. At my community pool whenever anything is even slightly amiss the lifeguard is supposed to give three sharp whistles which in turn alerts the entire crew of 20 or so lifeguards each stationed at her own corner of the pool [yes the pool does have 20 or so corners] to also emit three sharp whistles, repeatedly, while pointing in the direction of the other lifeguard whose whistle it was that alerted them.
That way, in the midst of the cacophony of whistles you can look at any random lifeguard, see where they are pointing, follow the trail of shrieking, pointing lifeguards until you find the root of the tree and then you know where all the trouble is. At least that’s the theory. Meanwhile over the loudpseaker the lifeguard who appears to have been selected for this job on account of having the most panic-stricken-yet-somehow-deeply-caring voice is sooth-screaming “Attention swimmers. Three whistles have been blown, please leave the pool. 7 year old Dennis is missing. He is wearing a red swim suit, a blue mask and snorkel. He is not wearing his plastic pants.”
This is followed every 30 seconds or so by further announcements of additional information that might be useful to us in our search for Dennis, “Attention swimmers [she hasn't seemed to have noticed that we stopped swimming 5 minutes ago and in fact we are now more appropriately addressed like "Attention patrons who were previously swimming and who are now digging through your beach bags for earplugs"] we are looking for Dennis. Dennis has a My Little Pony beach towel and he was last seen by his 5 year old sister when she was holding him down so his friends could give him a plastic pants wedgie.” Then “Attention swimmers, we are looking for Dennis. Dennis is going through a bed-wetting phase at home.”
Finally Dennis, who of course had just been undergoing repeated Whirlys in the bathroom emerges and the whistles fall silent but the cackling doesn’t.)
But the “Adult Safety Break” has very little to do with adults and nothing at all to do with their safety. Every 90 minutes all children under the age of 16 are required to leave the pool for 15 minutes. In the meantime, adults can swim but since nobody goes to this pool to swim in the literal sense of prostrating and propelling yourself through water with a well-defined origin and destination, what happens instead is that all of the adults leave the pool too and the lifeguards are the ones that get a break.
And that is precisely the rationale. Not the break for the lifeguards, but the temporary evacuation of the pool. Now note that this is a community pool, run by the community association so we have a situation in which the community is voluntarily destroying 15 minutes of pool value. So there must be a good reason.
And the good reason is that admission to the pool is by flat fee with no marginal time-use pricing. This means that the admission fee can be adjusted only to meter the number of people entering the pool but it provides no means to stop them from staying all day long. And indeed while their marginal value declines over time it appears to stay bounded away from zero until either nightfall or lightning strikes, whichever comes first.
The safety break makes us decide whether its worth it to sit through 15 idle minutes before climbing back onto the marginal utility slide. A large number of families by now already on the very flat end of that slide, its no wonder that the safety break culls a significant segment of the pool’s patronage in one fell swoop. It helps that the safety break consolidates all the kids in one place making the exit that much easier.
Bad for them but good for the community at large. Their tiny residual marginal utility is dwarfed by the externality of their presence multiplied by the number of other swimmers in the pool. Absent any way to expose them to their externality through prices, a community-imposed waste of time is the second-best solution.
Unfortunately for Dennis though, giving Whirlys only gets better and better.