Provided is a fuel composition prepared by adding gas-to-liquid oil and water to light cycle oil to conduct emulsification. The fuel composition is used as a fuel for a diesel engine (12) in a ship (10). The ship (10) includes a fresh water tank (15), an LCO tank (13), and a GTL tank (14) configured to store water, light cycle oil, and gas-to-liquid oil, respectively, and a mixer (16) configured to mix the water, the light cycle oil, and the gas-to-liquid oil fed from the respective tanks to produce the fuel composition.