Abstract: This invention is directed to an integrated onboard hydrogen (H2) production and utilization system for all watercraft, which yields environmentally benign vessel power production without new infrastructure requirements. Water (H2O) is supplied to a vessel, whether ashore, docked or underway, and is systematically converted into hydrogen and oxygen. The energy required for this process may be provided by any renewable or non-renewable source. The H2 produced is either utilized at once or stored. Energy is released from the H2 by one or more power plants.