This is a good survival mystery horror film, Sandra Bullock and others were well-casted. I like that even we the audience can't see the entities it makes the atmosphere even more creepy. the cinematography was wonderful especially the river sequences, and the editing was amazing, jumping back and forth from the current situation to the past and vice versa worked well. But what i didn't understand is that some could "see" and nothing would happen to them, did they adapt or something? it wasn't really explained here nor the origin of the entities for that matter. And the ending was a bit weak.