Water that you find when you are in a survival situation, inside a river, or perhaps a lake, or perhaps a stream, should not be consumed, since it is full of bacteria and infections. You need to boil the water you find in a river or lake to make it drinkable. So, boil the water for 5 minutes, then it is safe to drink. Here is an ingenuous way to convert bad water into drinkable water that a little longer to product water. But I found it very ingenuous.