Tidal stream marine energy comes from horizontal water currents that are created by the vertical variation of water levels caused by tides.
These currents affect areas where tides act in opposite ways (high tide on one side, low on the other) and the flow changes direction with tide level changes. In this case, the main energy is captured from a horizontal current of water, similar to what occurs to capture wind energy.
The machines able to use and capture this energy (Tidal Energy Converters) are mostly three-bladed horizontal-axis turbines, suitably sized to work on the sea floor.
Its similarity with wind technology has helped the Tidal Stream sector achieve an excellent level of technological maturity. Current systems are much more advanced than wave energy converters: tidal stream marine energy is ready for large-scale use.