At the end of the official Grown Ups trailer, Adam Sandler, David Spade, Chris Rock, Rob Schneider, and Kevin James are seen wallowing in a swimming pool at a water park. James's daughter approaches and asks, "Dad, are you making a sissy? You know they have a chemical in the pool that turns urine blue." James responds, laughingly, "No, no, no, that's an old wives' tale, sweetie." After which, of course, the camera zooms back, the child screams, and we see that all five men are surrounded by dark clouds of "sissy." End joke.
But wait — the chemical that turns urine blue actually is an old wives' tale, isn't it? Vulture, a blog that has only ever swum politely in pools, investigates.
An e-mail to "the Poolman" of Poolinfo ("the most useful source of swimming pool information online") was met with a definitive answer:
You are speaking of a product that is an urban legend. There is no such product available.
Case closed! (Although there is a product "to color the water in your pool for a short period of time," although, alas, it is merely "for decor.") So, everyone can now continue contaminating swimming pools without lingering fear of exposure by chemical detection. You are, however, disgusting and terrible people.