Magic in the Water (1995) on Netflix

Plot summary

Radio psychologist Jack Black's daughter Ashley keeps a recording of his show; she wants his attention, and his work always comes first. He takes Ashley and her older brother Joshua to Glenorky, a small Canadian town whose lake draws tourists with stories of a monster called Orky. Their cabin sits beside that of an elderly First Nations man. Jack meets Dr. Wanda Bell, a local psychiatrist who is helping a support group of men who say Orky's spirit has possessed them. While Jack works, the children look into the legend, and Ashley runs away. Jack, searching for her, has the same experience the men describe.