Far North (Vintage Paperback) by Will Hobbs

"Mayday! Landed on river. Engine out.
Floating toward the falls."

When the engine of their float plane fails during a water landing near the head of Canada's monumental Virginia Falls, what began as a sightseeing detour turns into a survival mission for two high-school students and their elderly companion.

With the brutal sub arctic winter about to fall like a hammer, Gabe Rogers, his boarding-school roommate, Raymond Providence, and Raymond's great-uncle, Johnny Raven, are trapped in a deadly wilderness. Braving icy rapids and desperately hunting for moose in their struggle to fend off starvation, all three travelers must rely on the others' knowledge and courage, or survival is out of the question.