This paper presents an optimal sizing of a marine current energy-based hybrid microgrid. For this purpose, a particle swarm optimization (PSO) has been developed on Matlab Software. An energy management strategy that takes into account the availability of renewable energy and energy consumption at all times has been implemented to meet demand throughout the year. In order to test the performance of the PSO, the results were compared to those obtained by the genetic algorithm (GA). The standard household load profile is selected to model an island residential loads variation. The Alderney Race (Raz-Blanchard in French)site is chosen as a case study for our marine energy system because its currents are among the highest in the world.