Her reasoning is inconsistent. What about places where the water does stagnate and it's dirty or at least dirty looking? Who made it that way?
And I strongly second Giles Gray's point. I had the venomous snake question about 40 years ago before I was baptized. I presented it to mature JWs who tried to offer feeble answers that I quickly shot down. I was told to just hold the question and that I would soon get an answer to it. Forty years later, and I'm still holding.
And back to the JW inconsistency...
Magnum: Wow! Isn't it amazing how the shape of that camel's red blood cells help it to go long periods of time without drinking water and then allow it to drink huge quantities when it does drink?
JW: Yes, and who made it that way?
Magnum: Wow! Isn't it amazing how that pit viper seems amazingly designed as a killing machine - with its fangs, venom, infrared sensors, jaws that allow for swallowing large prey, etc.?
Magnum: And who made it that way?
I'm not an atheist (I agree with what slimboyfat wrote); I just believe in consistency. JWs selectively apply logic and reason, and they selectively use evidence.