This is a tip from the show Survivor Man on The Discovery Channel!
This video will teach you how to kill bacteria in dirty water, in the wild, with only a plastic bottle, a string and a lighter or match.
Original video link
Step 1: Finding water in the wilderness without a stream or running water
For this instructable, we're assuming all you have is a lighter (or matches), a piece of string and an empty water bottle. Any container will do as long as it holds water.
If you can't find a stream or source of running water, look for a mud puddle. If you can't find a mud puddle, try to dig a hole deep enough so water seeps in the hole.
NOT SHOWN: As an added way to filter the dirt, you can place a shirt or piece of material over the opening on the bottle and use it as a filter to prevent large pieces of dirt from entering the bottle as you fill it.
Fill the container with water from the hole.