The Open Water Project aims to develop and curate a set of low-cost, open source tools enabling communities everywhere to collect, interpret, and share their water quality data. Traditional water monitoring uses expensive, proprietary technology, severely limiting the scope and accessibility of water quality data. Homeowners interested in testing well water, watershed managers concerned about fish migration and health, and other groups could benefit from an open source, inexpensive, accessible approach to water quality monitoring. We're developing low-cost, open source hardware devices that will measure some of the most common water quality parameters, using designs that makes it possible for anyone to build, modify, and deploy water quality sensors in their own neighborhood.