The objective of this paper is to present a summary of the state of the art in magnetic gear (MG) technology and then investigate its particular opportunities in marine energy device applications. As an introduction, a brief reflection on the state of the marine energy industry is given and the environment in which marine energy converters (MECs) operate is discussed. A brief overview of MG development over the past century is given and then the leading technologies are discussed in greater detail with the advantages of MG systems stated. In order to demonstrate the potential of MGs in marine applications the prevailing machines, i.e mechanically geared and direct drive machines, are examined in terms of sizing, reliability and economic value using previous studies on a similar technology, namely wind. Finally MGs are conceptually applied to three types of MECs to demonstrate how existing technologies can be quite easily adapted to incorporate the technology and gain the advantages mentioned.