These are very large ocean going vessels used to ferry people from or to countries. They are highly specialized vessels that are essentially floating hotels. There is a lounge for hosting parties, weddings and other exhibitions, large swimming pools onboard, basketball courts, bars,casinos, games hall,cinemas,a gym and many other facilities you will see in 5star hotels. These facilities onboard require a large amount of power to operate them. The ship is propelled by a gas turbine or diesel electric engine. The gas turbine is made up of a combustion chamber where the gas is compressed to a very high temperature and a series of turbine blades coupled to a shaft. The shaft is coupled to an electric generator. As the hot gases move from the compression chamber and flow over the blades, their impact causes the turbine blades to rotate. The mechanical energy of the turbine blades is then transmitted through the shaft to the electric generator which produces electricity. Diesel electric engines work the same way as gas turbines only that they use a direct drive system rather than a turbine.The output shafts are connected directly to the electric generator to produce electrical power. They both require fuel for power generation.