Vatnsá flows from Heiðarvatn to Heiðardalur in Mýrdalur, which is just above Vík. Vatnsá is a fun salmon and sea trout river that runs through a beautiful valley on its way down to Kerlingardalsá, where it merges before flowing into the sea. It is small and crystal clear and it is important to approach all fishing spots with great care, so as not to scare the fish.