This movie left me chilled to the bone, shaking. So much so that I felt compelled to watch warm fuzzy things before moving on with day-to-day activities.
I don't believe this reaction has as much to due with the scare/scream factor, but because of the growing dampness, the cold world, the sorrow, and the emptiness that Dark Water fosters.
This haunting film was apparently the inspiration for The Ring - and I can see why. Although the two are quite different, the underlining heart-breaking connection between both films is present and terrifying.
For full chill effect, I recommend watching this movie alone on a dark and stormy night.