The maritime industry is undergoing a significant transition from carbon-based fuels towards less environmentally harmful fuels. This transition is primarily being driven by international regulations calling for significant limitations on maximum-allowed environmentally harmful emissions. Hydrogen and fuel cells are often touted as one potential means for the decarbonization of the maritime industry. However, their adoption on board marine vessels is still in its infancy; some of the main reasons for the slow adoption being both high investment and operating costs. This dissertation proposes a new electric integration and operation concept for DC-based fuel cell-fed marine vessel power systems. The concept is designed to enable significant reductions in total powertrain energy losses, thereby reducing operating fuel consumption, which further leads to reduced vessel operating costs. The reduced cost of operation is highly beneficial in order to accelerate the adoption of fuel cells as main power sources for marine vessels, which in turn would also improve the environmental impact of the maritime shipping industry.