Off the Map by Meika Hashimoto

From Scholastic Press: Amos and Marlo have always been best friends. From hiking trips to backyard camp-outs, from playing soccer at the park to sitting together at lunch, they did everything together -- until this past school year, when it all fell apart. Out of nowhere, Amos stopped talking to Marlo, and she has no idea why. Embarrassed and angry, Marlo distracts herself by looking forward to an end-of-year canoe trip with her mom. A special wilderness adventure, just the two of them (and their dog). But when they arrive at the trail-head in the Alaska wilderness... there's Amos! Their parents have surprised them with a trip together. Things couldn't be any worse. During the trip, Marlo and Amos do their best to avoid each other at all costs... until their parents pair them in a canoe together. When they start arguing, Amos and Marlo don't notice that the grownups' canoe has disappeared. They've taken a wrong turn -- and they're heading straight for a waterfall. Lost in the wildernes