I watched this while working and then rewatched it after work to try to understand better. I also came to Google and reddit to try to make sense of this movie. I'm glad I'm not the only one who doesn't fully get it. From what I've read, i understand that David was possessed by the sacrifice but I feel like that wasn't portrayed well, I honestly just thought he snapped or something. There was a clue I guess when the wife goes into that dark room but it wasn't clear enough. If only a handful of people understand then it was a miss, also I think it's kind of pretensious to make fun of people who didn't understand. I feel like every possession wasn't clearly portrayed and like other people were saying there was too much bouncing around, first the boy is drowning, then he's fine, then he's missing, then he's fallen out the window, then his spirit is believed to be at the ship, etc. Too many timelines skips and it gets messy. Someone pointed out that there were only two timelines, sure maybe 2 main timelines but all the jumping around would mean that there are more technically.