This ocean science technology development project involves the design, construction, testing, and installation of a seafloor geomagnetic observatory at the Hawaii-2 Observatory (H2O) site located midway between California and Hawaii in 5000 m of water. The geomagnetic instrumentation to be installed meets INTERMAGNET standards for data accuracy and timing. It will consist of a delta Idelta D magnetometer, a gyrocompass for absolute direction measurement, a set of suspended magnet variometers, auxiliary environmental sensors, and a separate geoelectric observatory utilizing electrode chopping techniques. Power will be supplied by H2O and real-time, two-way communications will allow both control of the observatory from land and transmission of data to the user. The data from this site will be made freely available to the scientific community through INTERMAGNET. The geomagnetic observatory will also be a prototype for future installations at other sites.