As an avid fan of thrillers (horror too, if the horror is necessary to the story), I came across this title and, thanks to Amazon Prime, I was able to watch it. There's something to be said for the "backwater" / "out camping by the lake" horror genre, but "Backwater" is vastly different from the prototypes associated with that genre (e.g., Friday the 13th) - by a long shot.
I thought this was a very good film. The story is seemingly innocent in that the boyfriend/girlfriend duo decide to camp out by the lake, and, upon hearing a shout (they reference it as a "scream"), they begin to investigate, with each of them running into someone else. What starts off rather slow picks up in terms of tension, horror, and convolution about 1/3 of the way through. I jumped a few times, was mildly grossed-out a few times, and didn't see any of the twists coming 'round the bend! The style of filming is mostly single-camera, though frequently scenes take place at night and in thick darkness, and sometimes it was difficult to see these scenes. Definitely worth checking out!