12 Feet Deep (2017)

Two sisters are trapped under the fiberglass cover of an Olympic-sized public pool and must brave the cold and each other to survive the harrowing night. Bree, a diabetic, and Jonna, a recovering addict, are inadvertently sealed in when the pool manager locks up for the holidays. As the night unfolds, they face physical and emotional trials, revealing deep-seated secrets and traumas from their past, while a janitor with her own dark motives exacerbates their struggle for survival.