Nearly 2 billion people around the world still regularly drink water teeming with fecal matter and other pathogens, and more still suffer the consequences of contaminated pipes and storage units, as well as poor and irregular water treatment practices (not to mention fraud and illegal access). More than 600 million people still rely on unimproved sources, and even “improved” sources aren’t necessarily safe. Former pro surfer Jon Rose says he has a simple, $50 solution.