Marine engineeringmechanical engineering, although the modern engineer requires knowledge (and hands on experience) with electrical, electronic, pneumatic, hydraulic and even nuclear technology.
Marine Engineering staff also deal with the "Hotel" facilities onboard, notably the sewage, lighting, air conditioning and water systems. They deal with bulk fuel transfers, and require training in firefighting and first aid, as well as in dealing with the ship's boats and other nautical tasks- especially with cargo loading/discharging gear and safety systems.
The original term engineer on a ship meant the people who dealt with the engines ("The black hand gang"), as opposed to the Consulting Engineer concept. Marine Engineers are generally much more hands on, and often get dirty, sweaty and hot doing their jobs. Care and thought is required, however, especially with heavy machinery in a seaway, and in managing the rest of the engine-room crew.