I wasn't all that sure if what one smells as chlorine is due to urine. This
article seems to state that it's anything nitrogen based.
What you’re smelling are chemicals called chloramines, particularly one called trichloramine. They’re formed when the chlorine disinfectants in a pool react with nitrogen-based compounds in swimmers’ sweat, urine, hair, or skin.
Just wish people would stop using swimming pools and hot tubs/spas as a bath, or worse, toilet.