Davis’ contributions to oceanography span instrument development, field observation and theory. Developments include a current meter, surface and deep drifters, acoustic Doppler current profilers, profiling floats for mid-level Argo, a 6km-depth profiling float to expand Argo’s sampling, an effective multi-purpose underwater glider, Spray, a zooplankton camera for glider use, and gliders instrumented to explore the upper ocean food web. He has observed the ocean circulation, including a time series of western boundary transports, studied mixed layer dynamics, diffusion of particles, the coastal-upwelling overturning cell, and the relation of Solomon Sea transport to the ENSO cycle. He carried out early studies of array design (of MODE) and large-scale mapping using statistically optimized "objective mapping." He adapted that approach to the predicting climate variability from sea surface temperature. Davis' experiments are parsimonious and his analysis is elegant.