The Ucja comes into Slovenia from Italy and covers a distance of 6.1 km before it enters the Soca. It is a swift alpine river, but very inaccessible. Access is somewhat easier only at the country border and near its confluence with the Soča, below the village of Žaga. Its waters are inhabited by trout and Cottus gobio, while in the downstream parts of the river, grayling can also be found.
