Amongst all the necessities for survival, purified drinking water is one of the most critical. You can only survive about three days without water, less if you are trying to survive in a hot climate. That makes water a very high priority.
When we’re talking about pure water, that’s not the same as clean water. You can find a lot of clean water around that’s not pure. The cleanliness of water usually refers to how clear it is. But when we’re talking about purified water, we’re talking about water that doesn’t have anything living in it.