Waves and tidal streams contain huge amounts of energy, but the conversion technologies required to produce power are not yet mature. However, recent advances have led to a number of prototype installations, bringing the technologies close to commercialisation. There are several possible ways of operating, but as yet no clear consensus on the best solution.

The highest wave energy densities are in the Atlantic Ocean, with 40 to 60 kW per meter width of wave front. In the North Sea the highest wave energy resources can be found around the Orkneys, Shetlands, and off the coast of Denmark (up to 16 kW/m). The Mediterranean Sea also offers some suitable locations, for instance in Greece. Areas with lower wave energy may still be economically feasible, for instance in combination with other technologies (wave/tidal or wave/wind).

The best potential for tidal streams can be found in constrained water passages and around islands where there are large tidal flows. This makes tidal stream technology more site-specific than e.g. wave energy. Around the North Sea the potential for this technology can be found in coastal waters, inlets and around islands, e.g. around the Orkneys and Shetlands, the Norwegian fjords, Skaggerak (DK), the Wadden Sea (NL, DE) and Zeeland (NL).