Many of the problems in the movie had could have been solved by having a tighter plot, and characters who's action made a little bit more sense within the stories context.
Like if you set the movie in the stone age, the movie's "horror monster" would have simply starved to death from lack of ingesting metal. I'm not sure what the screenwriters were thinking, but stone and water could have been a major plot point earlier in the movie. But instead, other tactics were used to prolong for the three hours that it felt like.
I'll have a more in depth review, as soon as I finished transcribing my notes.