Anthropogenic electromagnetic fields (EMFs) have been introduced into the marine environment around the world and from a wide variety of sources for well over a century. Despite this, little is known about potential ecological impacts from EMFs. For decades, power transmission cables have been installed across bays and river mouths, and connecting near-shore islands to the mainland, with little consideration of possible effects to marine species from EMFs. At a time of greater environmental awareness, the US now faces the possibility of a new source of EMFs over a much greater extent of the seabed from offshore renewable energy facilities in coastal waters. This literature review synthesizes information on the types of power cables and models the expected EMFs from representative cables. Available information on electro- and magnetosensitivity of marine organisms, including elasmobranchs (sharks and rays) and other fish species, marine mammals, sea turtles, and invertebrates is summarized and used in conjunctio with the power cable modeling results to evaluate the level of confidence the existing state of knowledge provides for impact assessment. Gaps in our knowledge of power cable characteristics and the biology needed to understand and predict impacts are summarized and form the basis of recommendations for future research priorities. Potential mitigation opportunities are described with a discussion of their potential secondary impacts as well as suggested methods for monitoring mitigation effectiveness. Finally, because interest in offshore renewable energy has increased throughout US coastal waters, there is a concern that organisms could be exposed to multiple seabed power cables. Cumulative effects of this exposure are discussed.