Lac-à-Jim is a narrow and deep lake that stretches over 11.2 kilometres. At its widest, the banks are spaced only 0.6 km apart but it contains pits exceeding 40 metres deep.
Many species of fish live here: landlocked salmon, walleye, pike, lake trout, monkfish, smelt, whitefish and many others.
This lake owes its name to an Indigenous person who settled here in the 18th century: Jim Raphaël. When a missionary father discovered the camp, he baptized the children, including Jacques (nicknamed Ti-Biche) and celebrated mass.