Wyatt Russell portrays "Ray," a man who’s received an MS diagnosis and is now searching for a suitable home for his wife and two children. They settle into a neglected property featuring a sizable swimming pool, and the story begins there. Following the removal of some disquieting sludge from the plumbing, they discover the pool's water originates directly from an aquifer and might contain minerals beneficial to Ray’s condition. Remarkably, it seems to help! His health noticeably improves with regular swims, but his family grows convinced that the water is connected to something sinister. Each member experiences a disturbing presence which leads his wife, "Eve" (Kerry Condon), to seek out the previous owner. This individual eventually and rather ominously verifies what she’d already found through an online search! It seems this pool offers a blessing but demands a terrible price—regardless of how you characterize it. The film moves along at a decent pace, avoiding elaborate special effects; instead, the sound design, intermittent lighting, and often obscured water create the unsettling atmosphere as the audience gradually pieces together what’s happening. While the performances aren't particularly strong and the writing isn't exceptional either, I still placed it on the more frightening side of Blumhouse’s horror offerings. It would be a better experience in a large, darkened theater; watching it at home would likely be quite ordinary.

Source on TMDB