We describe the use of a multi-metal electrochemical cell for measuring ocean pH. The sensor was designed to be robust, inexpensive, and capable of 0.02 sensitivity to pH in the narrow ranges required for marine pH monitoring. A prototype sensor has undergone an extended ocean deployment with promising results. My role consisted of structural waterproofing and tracing leaks, and achieving neutral buoyancy with attention to weight limitations. We presented our solution in Monterey Bay at the Wendy Schimidt Ocean Health Prize summit in December, 2014.