The inherent diversity of the multitude of vessels plying rivers, lakes, harbors and oceans around the world extends past size and shape and type of service - at the heart of each vessel is a propulsion system. Although propulsion systems may often be considered unique, a variety of typical solutions for most types of vessels already exist. In some cases, it may be preferable to simply specify the duplication of an existing propulsion system, allowing a degree of harmonization in the number of required spares, trained mechanics, and maintenance. It would seem, however, that ship owners and operators are placing an increased premium on designs and solutions both unique and innovative, in order to reduce costs and maximize performance.