I've read some reviews here that say the movie didn't explain anything at the end. But the movie doesn't have to explain anything because the story is already pretty clear.
First of all, the positive aspects...the actors are great, especially Eliza Scanlen and Dylan O'Brien. The sound and the set also create enough of a mysterious atmosphere and the viewer is drawn into the story and the characters.
Here come mega spoilers: But as it was so beautifully said in the movie "The Repeaters", "Don't fudge with time" and plenty of that happens here.
For all those who didn't understand the story. The swamp area has a kind of time jump zone where you end up in all those years, where there's drought, so to speak, and where Anna has her seizures. Anna is the daughter of Celeste's second husband, Ellie's half-sister and also her grandmother, because Ellie's father Paris, Celeste's first husband, jumps back in time with her to 1952. That's why Ellie tells her stepfather Daniel that they are family, because Daniel is also Ellie's "grandfather" and Anna is Celeste's stepdaughter and her ex-mother-in-law at the same time. Simple, isn't it?
The point I don't get though is that theoretically Ellie could "pick up" her dad Paris in this swamp wormhole time jump zone and save him from death...so the whole "family construct" would be even more obscure than explained...that's why time travel movies are so both understandable and yet nonsensical at the same time.
Voir plus 
