Wave power is one of the most rich and promising sources of renewable energy for the future. Approximately 2000 TWh/year can be produced through the exploitation of the wave energy potential. In the past four decades, hundreds of Wave Energy Converters have been proposed and studied, but so far a conclusive architecture to harvest wave power has not been identified. Many engineering problems are still to be solved; these include survivability, durability, and effective power capture in a variable wave climate. Reacting body devices use the inertia of a large mass to generate the reaction needed from the power take off (PTO). Heretically, in the case of a simple inertial mass, optimal control adjusts the dynamic parameters of the PTO, such as the spring constant and energy absorbing damping, to maximize energy absorption. The ISWEC (Inertial Sea Wave Energy Converter) uses a gyroscope to create an internal inertial reaction that is able to harvest wave power without exposing mechanical parts to the harsh oceanic environment. In the past few years, the ISWEC has been successfully tested using two scale models (scales 1:45 and 1:8) and several extensive laboratory experimental campaigns. In this paper, the first full scale ISWEC prototype is presented along with its control system and a refined control strategy. The goal of this paper is to identify an optimal control strategy in order to maximize wave power exploitation of the ISWEC. The control technique presented is numerically applied to the ISWEC full scale device with rated power of 60 kW. The control strategy is tested, and the expected production obtained, for the typical wave climate of Pantelleria Island, in the Mediterranean Sea where the first full scale ISWEC prototype was deployed in autumn 2015.