The first commercial tidal energy project in North America is in its final test phase.
Turbines have been engineered a little way off the coast of the US state of Maine, in such a way as to ensure that they always turn the same way, whether the tide is rolling in, or out.
The turbines power a generator, creating electricity. Cables carry it onshore and directly into the power grid.
Three years from now, authorities hope that hope that the generator will power 1,200 homes.
Al Jazeera's Scott Heidler reports from Eastport, Maine.