The Mer Bleue Lake (length 5.5 km, altitude: 208 m), located in the municipality of Cayamant, Quebec, is the main body of water of the head of the Aigle River.

From there, the current runs eastward through a short strait of about 120 m, which separates the latter lake and the "Lac Lacroix" (which is shaped elbow, 2.8 km long).

From the outlet of the Strait, the current crosses Lac Lacon, 0.7 km east, bypassing a peninsula emerging from the south shore, to the entrance of the strait connecting the "Lac de l 'Eagle' (2,2 km long, altitude: 208 m).

The Eagle is a large daytime bird of prey with hooked beak and powerful claws.

The toponym "Eagle River" was formalized on December 5, 1968, at the Bank of Place Names of the Commission de toponymie du Quebec.