The Wave Glider, a wave-powered unmanned maritime vehicle (UMV), represents a novel and unique approach to persistent ocean presence. Wave Gliders harvest the abundant energy contained in ocean waves to provide essentially limitless propulsion. The Wave Glider can operate as a vessel, covering long distances in the ocean, or as a station-keeping platform. Wave Gliders have demonstrated long open-ocean transits and extended deployments of up to one year. The High-frequency Acoustic Recording Package (HARP) is an autonomous data logging system optimized for long-term, broad-band marine mammal monitoring. The HARP system includes low-power electronics, high-speed data sampling, large capacity data storage, and batteries for self-contained power. In addition to housing the data logger, a hydrophone was designed to be towed behind the Wave Glider. Together, Scripps Institution of Oceanography and Liquid Robotics combined these two technologies to demonstrate a new approach to marine mammal monitoring. Providing a mobile, long-endurance and fully connected platform for acoustic monitoring, the Wave Glider with HARP enables new scientific results and improved economics. Over a series of engineering and scientific evaluations, the HARP system has proven effective for monitoring marine mammals when deployed on the Wave Glider. In this paper, we give an overview of the Wave Glider platform and integrated HARP system, and present results from the extensive engineering sea trials conducted with several prototype and production versions of the vehicle and data logger.