Marine hydrokinetic (MHK) power is likely to play a crucial role in future energy diversification and remote energy supply efforts. Providing a means of direct energy storage for MHK power would provide additional benefits to applications in ship microgrids and remote communities. Hydrogen (H2) has long been pursued as a means of green energy storage and can be generated through electrolysis of water in an electrolyzer. However, electrolyzer technology for H2 production is currently only possible on the commercial scale using fresh water, also a precious resource in our society. The direct electrolysis of seawater would alleviate the fresh water constraints for a new H2 feedstock and a seawater-fed electrolyzer could be powered locally at a MHK platform. Several technical challenges exist before efficient direct seawater electrolysis can be realized. This project was designed as a demonstration of efficient direct seawater electrolysis that limits chlorine evolution, avoids use of platinum (Pt) group metals and overcomes cathode fouling over long service times.