Decent watch at best, could watch again, but probably won't, and can't sincerely recommend.
I had to watch this twice to make sure I followed what happened, I thought it was because I was really tired the first time, but nope, it made about as much sense the second time.
A lot of this is just the writing. I don't know what is with writers and mysterious islands (I'm looking at you, "Lost"), but it makes them crazy: just because ANYTHING could happen, doesn't mean it needs to. The problem with "Lost" is that they were actively reacting to viewer reactions, trying extremely hard to produce episodes that didn't match predictions (allegedly keeping the audience guessing), but that just makes disjointed story lines that wildly diverge for no reason. This movie is basically that happening all in one go.
The reason that the audience can draw lines is because a pattern is established by the written story, diverging breaks that pattern; it does not enhance it.
This movie keeps some movie mystery clues in there, but there is a LOT of wild diverges and acting within acting here that I can't elaborate on without spoiling it (it's the one "great" thing about this movie, so I won't). There is a high quality way of writing that involves red herrings and proper misdirection, but this is not it. The end result looks the same, until you review what happened and realize that the first was based off the information given and the second is based off of arbitrary writing decisions.
The mystery of the island itself interferes with the traditional mystery aspect as well. Even in ghost mysteries there are rules to follow. When there aren't any rules left, you can't predict and the story actually gets boring if not frustrating.
I am not saying this movie is without worth, but I am going to say that I feel bad for Lucy Hale as she's definitely the best of this movie.