If there was ever a horror movie that could be called the cinematic equivalent of fast food, "Lights Out" would be a fat, juicy cheeseburger. You savor every delicious morsel as you consume it, but afterwards you're self conscious about what you just allowed into your body.
"The Shallows" seems to be an attempt to forge a marriage between critic friendly drama ("Open Water"?) and plebeian friendly entertainment ("Shark Night"?), although the relationship ends up being somewhat turbulent, if passionate.