Beneath Still Waters (2005) on Netflix

In 1965, in Northern Spain, a dam will be built to bring progress to the location of Desbaria and the town of Marienbad is near to be completely flooded. Two boys, Teo and Luis, cross the security boundary to play in the evacuated town and Teo listen to voices in the abandoned church. They find a group of strange people chained in the watered basement, Teo releases their leader Mordecai Salas and is killed by him. Forty years later, in the celebration of the fortieth anniversary of Debaria Dam, the teenager Antonio vanishes in the lake while swimming with his girlfriend Susana and their friend Clara Borgia. The police divers, with the support of the outsider cameraman journalist Dan Quarry that is filming the submerged Marienbad to write a matter about the town, try unsuccessfully to find the body. When eerie things happen in the spot, Dan and the local journalist and daughter of the builder of the dam Teresa Borgia disclose dark secrets about Marienbad, Salas and his evil cult of the power of the flame.

—Claudio Carvalho, Rio de Janeiro, Brazil

Two boys make a pact to do something brave, crazy and dangerous. They will see their town one last time before a man-made lake floods it forever, burying it under the deep lake. Everyone's been evacuated - just the church, the homes, the abandoned shops remain. Only the eerie buildings...still hiding secrets that no one suspects. The two boys walk through the doomed ghost town. But the boys discover that the town isn't quite deserted. And they are trapped as a massive wall of water crashes down on the town. Time passes, and the whispered secrets of the town have been long forgotten. But now, fifty years after vanishing, the sunken town comes alive again. A boy vanishes swimming on a moonlit night while his girlfriend looks on. The very shoreline turns hungry, pulling people into the water. And below-below where it's incredibly cold and dark, the sunken town waits. Because beneath still waters something ancient now stirs. A forgotten legend lives again. Half a century ago they thought they had buried this horror forever. But you can't kill what was never really alive. And the massive stone walls of the Dam must soon burst and what was an incredible myth, will become a deadly reality.

—Filmax International