SPOILERS AHEAD, SPOILERS AHEAD! SPOILERS AHEAD!
Many people posted bad reviews for the movie because they think it is full of plot holes, If you are one of these people please send me a private message with your plot holes and I will do my best to explain them to you. Some say the main actress acted irrationally without going into detail as to WHY or HOW, again please message me and I will explain.
I will attempt to explain some of the major "plot holes" that people think this movie has. I copied and pasted some questions word-for-word from a review that I already read which were common amongst other reviews.
Here's a brief transcript in the movie, it is relevant to my explanation:
Come check this out. This is the same ship. This thing's old. Jess. Oome on. Oome on. Here's where we boarded. Oh, yeah. Aeolus. Aeolus was the Greek god of the winds and the father of Sisyphus, the man condemned by the gods to the task of pushing a rock up a mountain and let it see roll back down again. That's a shitty punishment. What did he do? He cheated Death. No, he made a promise to Death that he didn't keep. I studied it but I can't remember.
1) What happen at the end when they got into the car crash, and she's perfectly fine?
She was wearing a seat belt, while her child was in the back seat without a seat belt and therefore died. If you're wondering why she didn't put a seat belt on her child, see explanation of question 3. Sometimes a seat belt is the difference between dying and walking away without a scratch.
2) Why is it that nobody sees her except for the taxi driver?
The taxi driver is death, and he is the reason the loop is happening, if you look at my transcript you'll see that "He cheated death, no, he made a promise to death that he didn't keep". By killing herself and staying alive, she cheated death... Also as she is leaving the taxi, he asks if she'll be black, she says "Yes, I promise", she knows that she can't really be back (as in from the harbor, which is what the taxi driver REALLY asked her), so she made a promise to death that she couldn't keep. If you go re watch the scene where the taxi driver walks up to her for the first time, you will see the colors dim, the movie gets dark, and the music becomes ominous. The taxi driver is death, and this is why he was the only one that can see her.
3) If she remembers everything. She knows exactly why she's going on the sail boat (apparently to go back in time to save her kid), then why is she doing the same thing over and over again?
The loop does not happen the EXACT SAME WAY every time, you can see this by the scene where she discovers the bodies of one of her victims, they are strewn all over the place, indicating that the loop happens differently every time.
Perhaps the last time the loop happened, her child died in a different way, which is why she isn't EVER able to stop her child dying. For example, when she goes to pick up the dead seagull after hitting it, maybe her child opens the door and runs across the freeway, and dies... maybe in other loops its a heart attack... etc.
The only thing wrong with the movie is that she should have been much more paranoid about her child in the end, because she should know that he can die in various ways. Maybe some part of her knows, that, as the taxi driver said "There's nothing anyone can do that's gonna bring him back.", but chooses to continue the loop by going to the harbor because she doesn't care, she would rather live with the faint glimmer that maybe at some point she can save him.