The potential of generating electricity from marine tidal currents is enormous. Tidal energy is a renewable source that has an additional value in a future energy market with regard to other renewable energy sources thanks to its high predictability. Moreover, tidal energy technologies are characterized by CO2 emission-free power, thus enabling energy security and contributing to economic growth and job creation in coastal and remote areas. Substantial progress is currently,being made by the European Union as regards the reduction of greenhouse gas emissions, renewable energy and energy efficiency, in order to fulfil the target of an installed capacity of 3.6 GW of ocean energy by 2020, and to achieve a future installed capacity of 188 GW of ocean energy in 2050. This paper presents a comprehensive review of the current status of tidal energy conversion technologies and describes the costs incurred in the development of tidal energy projects so as to study their economic viability. The study also identifies the principal current risks and the role of each of the stakeholders involved in the successful development of tidal energy projects. Finally, future challenges in tidal technologies that will influence the increase in their current potential are briefly presented along with the current developments of our research group in the field of tidal energy converters design.