Oceanographic research organizations frequently make use of electronic sensors to monitor ocean conditions such as temperature, acidity, and dissolved oxygen. Presently, these sensors are powered by batteries, but this causes their deployment time to be limited by battery life. Harvesting energy from the environment in situ with the sensors is a potential means of overcoming this limitation. Where sufficient energy is available from the surrounding environment, maintenance-free deployment times could be greatly increased.We have identified ocean currents as a potential source of energy that is available in a wide range of marine environments. This source is novel, and may be available where other sources like solar and wave energy are unreliable, such as at extreme latitudes and depths. To assess the feasibility of ocean currents as an energy source, we performed a theoretical analysis using fluid mechanics and thermodynamics principles. Our analysis suggested that a meter-scale device could extract power in the 1-10 W range from currents as slow as 0.2 m/s. Having established that power generation in that range is suitable for many sensor installations, and given that speeds of around 1 m/s can be found in major ocean currents, this was considered a positive result. Based on this positive indication, we proceeded to develop an ocean current energy conversion device for powering ocean sensors. The device is based on a meter-diameter open-flow turbine with an alternator in a direct-drive arrangement. We have run CFD simulations to predict and optimize the performance of the device. We have also built and tested the alternator to characterize its performance. CFD and testing results so far continue to support the feasibility of the device. Construction of a complete prototype is underway and testing in a tow tank is planned.