The diversity of marine environments from which we may begin to tap tidal energy has ensured that no single technical development is likely to emerge that can solve all our tidal energy extraction problems. No one system is likely to be suited for every location. At present, the industry is following up a range of experimental devices. No system has demonstrated itself the clear technological leader. Shallow tidal estuaries can play host to extreme tidal ranges. It is the high tidal range that barrages and their concept offspring such as artificial lagoons and impoundment basins use. All other tidal devices fall into the category of harnessing kinetic energy from tidal currents, or what is being talked of as “tidal stream”.