When Tom loses his grip on the cliff and plunges into the river, the cliff face is actually gray fabric painted to look like rock. If you look carefully, it moves and bounces like fabric as he rolls down it.
After Tom jumps off cliff into the river he coaxes the family dog, a yellow lab named "Maggie", into jumping in after him. Throughout the entire movie the dog is called "Maggie" and referred to as "girl" but when the dog leaps from the cliff into the river, you can clearly see it's a male dog.
At 30:02 they are supposedly traveling alone through the wilderness. However you can clearly see in the background several people playing and fishing by the riverside with an aluminum rowboat up on the bank..
Throughout the movie, Gail warns the bad guys that there's no way out of the canyon other than via the Gauntlet, which only she can navigate. But Wade threatens to shoot her anyway. Moreover, Tom, the dad, runs ahead the boat and past the Gauntlet.