The surface of the "Nepton North River" is usually frozen from early November to mid-May, however, safe ice circulation is usually from mid-November to mid-April.

The "Nepton North River" originates at the mouth of an unidentified lake (length: 0.8 kilometres (0.50 mi) altitude: 499 metres (1,637 ft)) in the township from McCorkill.

This lake is located northwest of a mountain with a peak of 595 metres (1,952 ft); this summit corresponds to the limit of the MRC Eeyou Istchee Baie-James (administrative region of Nord-du-Québec) and Lac-Saint-Jean-Ouest (Saguenay-Lac-Saint-Jean) This source is located at: From its source, the Nepton North River flows over 6.4 kilometres (4.0 mi) generally to the southwest.

From the mouth of the Nepton River, a peninsula is advancing in a straight line on the south-west in the bay to the outlet of Forest Lake.

The mouth of the Nepton River is located at 0.4 kilometres (0.25 mi) east of the boundaries of Roy and McCorkill Townships.