Not wanting to branch out into a different area of discussion, but the reason for the concern in the U.S. is the anthropogenic factors that have been thrust upon nature over the past century that has resulted in 90% of natural waterways being polluted to some extent. This is what is behind the present governmental mind set of preventive action to protect human health.
Let's face it, the natural earthen pond of 2012 does in no way, as far as water quality is concerned, resemble the natural earthen pond of 1900.
One other factor that I would consider is liability. If you don't follow government guidelines and you declare or imply that the pond safe for swimming, you could possibly find yourself in court trying to save your company if someone, especially a child, becomes ill.
Keep us updated.
"Everybody is ignorant, only on different subjects." - Will Rogers