If you’re stuck in the wilderness with no UV pen, stove, or chloride tablets, there are still ways to decrease your risk of swallowing a nasty bug. First, forget the myth that running water is safer to drink. That’s just not true. “Even water that looks clear and clean isn’t always that way,” says Nicolazzo, who has suffered from both dysentery and giardiasis and has spent 45 years in the wilderness education industry. Often, you’re better off collecting water from a foot below the surface of a large, clear, not stagnant lake—though that’s still not free from risk. Be especially cautious of streams or rivers during the spring, when melting snow carries animal and human waste that was deposited over the winter, downhill.