Freshwater is the lifeblood of Europe. And yet, from Estonia's peat bogs to the crystal-clear waterfalls of Plitvice, the continent's salt-free waters couldn't be more different. In French river, catfish stalk unsuspecting pigeons, while pelicans in the Danube Delta battle cormorants for the best fish. On the River Meuse, a pair of beavers patiently build a lodge for their adorable pups – a far cry from the chaos of millions of Hungarian mayflies all trying to mate on their only day of life.