Stream okay or not?

We've had a lot of good water time this summer.  Pools, oceans, even streams at parks.  Ansel walked right into a stream at a local park recently.  I let him do it. Then Ollie joined.  They played in the semi-stagnant water and afterward we took baths. I think that was one of the best days they've had this summer.  The freedom and newness for them was invigorating.  What do you guys think of streams at parks? Yesterday I didn't let them do it because I did not want to take them to the bath right after.  Am I over thinking this or under thinking this? Are streams too germ-ridden? I am torn. What do you think?