Your metabolic rate can be several times higher in a pool or other body of water than it is on land without any exercise at all. Body heat is lost at a much higher rate when you are submerged in water and your body will burn more fuel to maintain core temperature.
This is something fighters do when they’re going extreme weight loss before a weight in. I’m addition to dehydrating themselves and eating clean, they have several different cold exposure methods that causes the body to burn more calories.
Swimming’s really good for losing weight, no sweating and less knee pain involved. Wish I had a private pool too, you can definitely tell the public ones are 30% filled with piss.
This is sort of how everything works, unfortunately! Guaranteeing 0% of something is really hard. Your flour probably has a small percentage of bugs in it, for instance. Urea is a relatively small molecule that I imagine you can find tiny amounts of pretty much anywhere. I would be unsurprised if there was at least one molecule of urea in literally anything you eat!
That said, dear god I hope I’ve never been in a pool that’s 10% urine :(. Those kiddie pools at the water park are probably like 90% urine, though. Sometimes I wonder if by volume adults pee in the pool more than kids, though. I have a suspicion a good chunk of adults think it’s fine or will do it secretly anyway.
It’s not even unfortunate. We’re a lot more robust than we think we are. We have two sets of organs designed to filter shit we consume out of us, and in quantities less than a certain amount, whatever it is isn’t noticeable. Also, chemicals used in public pools are designed to neutralize things like that. If the water isn’t noticeably tinged, you won’t even know the difference.