Since the late 1990s, there has been increased interest in marine renewable energy, such as wave and tidal current. Wave and tidal current energy has the potential to supply 15% of the UK’s electricity needs, and in the United States the potential is about 7%. Unlike wind, there is no single technological solution to harnessing energy from waves and tidal currents. As a result, many different devices are being developed, and so far there is no optimum solution. Because ocean energy systems operate in a harsh environment, there are significant engineering and environmental challenges to overcome. The UK Energy Research Centre Marine Renewable Energy Technology Roadmap classifies these challenges in terms of predictability, manufacturability, survivability, installability, affordability, and reliability. A number of centers and consortia throughout the world are working toward addressing these challenges, including the European Marine Energy Center (Scotland), SuperGen Marine Energy Research Consortium (UK), Hydraulics Maritime Research Centre (Ireland), Wave Hub & PRIMaRE (South West England), Northwest National Marine Renewable Energy Center in Oregon and Washington (US), the Hawai’i National Marine Renewable Energy Center (US), and the Fundy Ocean Research Centre for Energy in the Bay of Fundy, Nova Scotia (Canada).