The potential of electric power generation from marine tidal currents is enormous. Tidal currents are being recognised as a resource to be exploited for the sustainable generation of electrical power. The high load factors resulting from the fluid properties and the predictable resource characteristics make marine currents particularly attractive for power generation and advantageous when compared to other renewables. There is a paucity of information regarding various key aspects of system design encountered in this new area of research. Virtually no work has been done to determine the characteristics of turbines running in water for kinetic energy conversion even though relevant work has been carried out on ship’s propellers, wind turbines and on hydro turbines. None of these three well established areas of technology completely overlap with this new field so that gaps remain in the state of knowledge. This paper reviews the fundamental issues that are likely to play a major role in implementation of MCT systems. It also highlights research areas to be encountered in this new area. The paper reports issues such as the harsh marine environment, the phenomenon of cavitation, and the high stresses encountered by such structures are likely to play a major role on the work currently being undertaken in this field.