Beneath Still Waters (2005)

Forty years ago a Spanish town is flooded in the creation of a reservoir in order to bury the supernatural forces awakened by an evil cult.  Now there are a series of deaths and disappearances around the reservoir, accelerating until the entire town goes mad.

Good concept, pretty original and unpredictable, unfortunately ruined by poor dubbing and overambitious CGI.

Good enough to make you imagine a better mad movie with the same material.  On the plus side, I'm looking forward to reading the book by Matthew J. Costello, which you can get on kindle from Amazon.