Factual error: While Anthony and the two others are staring at the bear as it screams, you see a large cold-blooded lizard scuffle up the tree right behind the bear's head when the young man says, "C'mon, let go!" No way that would live in the area they're supposedly in. (00:44:35)
Factual error: Charles and Robert manage to outrun a charging Alaskan brown bear over a course of several hundred meters, leading it into a trap. This is absurd. The absolute maximum running speed of a human being is about 27 kilometers an hour, and that is for an appropriately dressed, fit athlete over a very short course on flat ground. They are in a rock strewn stream and are wearing heavy winter clothes. A fit, healthy, active male Alaskan brown bear like the one chasing them could hit 45 kmh in that environment without popping a sweat and could keep that up for a kilometer or more. When enraged or charging prey - as this one was - they have been clocked at 56kmh. This is nothing to do with an adrenaline rush - that will not enable Charles or Robert to exceed their body's maximum running speed by 200%.
Chosen answer: Although Bob intended to kill Charles (to obtain his wife and wealth), they unexpectedly were struggling for survival in the wilderness. Working together increases their chances of rescue, and Bob cannot survive without Charles' help. He therefore saves him from the rapids. Plot-wise, this makes Charles think that his suspicions about Bob may be wrong. Also, Bob is not a born killer, and may be hesitant about actually committing murder, particularly someone he had admired and respected. Bob likely planned to kill Charles when rescue was imminent and then claim Charles died accidentally. Regarding the title, because the movie is not based on a book of that name, the filmmakers probably chose it for its marketing value because it sounded dramatic. This is a suspense/adventure movie, and "edge" can have multiple meanings, such as being "on the edge," as to whether or not Bob will carry out his plan. It can also refer to the razor-sharp edge of a weapon, an "edgy" emotional situation, and so on.
raywest ★