Unless you've gone through life drinking nothing but Perrier delivered by your personal butler, you probably know better than to drink straight out of the first stream, pond, or gutter that you come across in an emergency. Even crystal-clear, clean-smelling water can contain millions of tiny bacteria, protozoa, and other waterborne pathogens that are invisible to the naked eye. And if the water you drink contains substantial amounts of those pathogens, you're going to be in for some serious misery. Passing the water through a filter such as a LifeStraw can strain out these harmful microorganisms — the YouTube channel Sci-Inspi shows the results of this filtration at 1000x magnification through a microscope.

After leaving some decomposing leaves, dirt, and water in a beaker for a few days, the Sci-Inspi video shows a sample of the dirty water under the microscope. Even at a relatively low 40x magnification, the results will make your skin crawl. Under higher magnification, the water is absolutely teeming with life.

This water is then drawn through a LifeStraw filter using a sterile pipette, and the results are clear — literally. Although this isn't a by-the-book test that precisely quantifies the number of remaining microorganisms, as required by NSF/ANSI test protocols, it does paint a general picture of why water filtration matters. Watch the 5-minute demonstration below, and keep this in mind next time you're tempted to drink some questionable water in the woods.

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For an overview of some of the options for water purification in a survival setting, refer to our previous articles:

• Solar Water Purification: Misconceptions and Facts
• Water Purification: The “Minimum Boiling Time” Misconception
• Improvised Water Filters: Not a Drop to Drink

Written by Patrick McCarthy