As farm kids we would jump in any old cow drinking pond filled with mud green water, frogs, snakes and cow dung. Never got sick in the tropics from local water or food.The only problem we had wasn't directly from the water, it was the blood sucking leeches. The ones in the water were bad but the tree drop versions were nasty. They would bleed you like a vampire.I don’t drink water outside unless I can see the source, it’s above 12,000 feet (tree line), there is no evidence of human activity above, it’s cold and it looks pristine. It’s worked so far.