Maritime vessels that recharge often or have enough battery energy storage capacity can achieve zero-emission operations using batteries alone. Unfortunately, for many vessels this is not the case. However, zero-emission operations can be achieved using battery energy storage together with a marine fuel cell system and a green fuel source, such as hydrogen. With this combination, vessels can maintain zero-emission operations for longer without refueling or recharging. When green hydrogen is used as the fuel source, water is the only system exhaust. The result is an efficient and environmentally friendly power source, ideal for operations in emissions-restricted ports, harbors and zones.