Multiphase generators seems to be an interesting solution for variable-speed drive applications and particularly attractive for renewable energy generation. In this context, the performance of a five-phase permanent magnet synchronous generator are evaluated within a marine current turbine and compared to a classical three-phase generator. For both topologies, a robust nonlinear control strategy, namely high-order sliding mode control, is adopted. Hence, the generators performances are analyzed, during open-circuit faults, and conclusions are derived regarding multiphase generators key features marine applications.