I imagine that the health effects of this practice in an indoor pool would be worse.
From Live Science:
They found that two chemicals, cyanogen chloride and thrichloramine, are formed by the reaction of uric acid [otherwise known as pee] and chlorine. When inhaled, these chemicals are known to affect multiple organs, including the lungs, heart, and central nervous system. So it seems that peeing in the pool has its own punishment — it’s just too bad it affects everyone.
Let's not make a "swill" out of the water we swim in. Encourage kids and teammates to be responsible.