Algae is a sign of high nutrients in the water. Myself if there was any water around me when I was a kid I was in it catching frogs turtles and snakes. The extra ear that I have growing on the back of my head is healthy so the Dr says .. Jk. for some folks they can swim In very nasty water and have no problems. Others may be more sensitive to water conditions and could have issues. Its all in the swimmer but I will say this if you question keep the eyes closed and don't take a mouth full.
