ELI5 Pee - is urinating in the pool ok?

Is it ok to pee in the swimming pool? Is pee poisonous or sterile? Which famous swimmers admitted to peeing in the pool? Why is it ok for sea creatures in the ocean, if all the creatures are peeing in there? How does urine indicator dye work? (hint it doesn’t)
... we explain like I'm five
Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: nybiggs, sciviasknows, wubaluba_dubdub, that_biology_guy, gumburcules and bananajesus
Details on the Canadian study we referenced:
https://www.theguardian.com/science/2017/mar/01/how-much-pee-is-in-our-swimming-pools-new-urine-test-reveals-the-truth
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