The Vydra river is the headstream of the Otava river. The wild mountain river with a stony bed runs through the nice valley, which is protected in the reserve called Povydří (Vydra Valley).
The river begins at the confluence of the Modravský Potok (Modrava Stream), Roklanský Potok (Roklan Stream) and Filipohuťský Potok (Filipova Huť Stream) near the village Modrava. The headstream of the Vydra river is the Modravský Potok stream, which springs on the north-western hillside of Luzný mountain (Lusen - 1,373 m) at an altitude of 1,210 m a.s.l.
Vydra joins the Křemelná river near the small village Čeňkova Pila. This is the beginning of the Otava river.
The Vydra is 23 km long (from the spring of the Modravský Potok stream to the confluence with the Křemelná river) and it takes water from an area 147 square km.
The red marked path leads along the river between Modrava and Čeňkova Pila. Its part between the settlement Antýgl and Čeňkova Pila is known as instructive path Povydří (Vydra Valley) and it leads through the reserve Povydří (Vydra Valley).