It flows for just 100 kilometres, but the Rance, a river in France's Brittany region, is still home to an exceptional and ever-changing biodiversity. Its mouth has been home to France's only tidal power station for half a century. We see how the 400-metre-long dam also acts as a road bridge between the towns of Dinard and Saint-Malo. Some 17 percent of households in Brittany get their power from this green energy source. We then take you further up the valley, where you can find boats, fishermen, old mills... and a famous seal named Joséphine.