Machineries on board ships include diesel engines, electrical generators, boilers, turbines, pumps, hydraulic machineries, refrigeration, air conditioning, electrical machineries, electronic equipments, etc, practically a mini city. Marine Engineers are involved in the running, operation and maintenance of all these machineries on board ships. Since they are in-charge of all the machineries on the ship, they get hands on experience on variety of machineries, which is normally not possible in a shore based industry. Promotions to higher ranks are based on passing examinations and experience. So if you are hard working, you may become a chief engineer of a ship after about seven to ten years of joining a ship as a junior engineer. This kind of promotion and holding high responsibilities in a shore based industry is normally not possible.