When you read alot of the 1 or 2 star reviews on here, you'll see theres a common theme that the reviewers missed the point of the movie. Alot of them say that the movie was just about a girl and her dad on vacation, and they might also mention the dads depressed. But this film is far more than that. I think to enjoy this film, you have to first have a better synopsis of it. The film is essentially about Sophie reminiscing on the past and thinking back to her final vacation with her dad and how she was completely oblivious to her dads depression. When you look at the film through these lens, it'll make more sense. I think having an understanding of depression also helps you spot the dads symptoms and makes the movie much more powerful. If you ever decide to watch this wonderful movie and you fear that you will miss the point, just keep in mind the word "suicide".
Another common complaint is that the ending didn't mean anything and that theres alot of random flashes on the screen.
(SPOILER ALERT)
At first when I watched the film, I always thought the ending was open ended. The whole movie was building up to Calem, the dad, suiciding but we never directly see it happen at the end. But upon revisiting the final scene and the movie as a whole, It's very clear that the whole movie was building up to his suicide as we see Calum cares less and less about life. When he steps into the room with the flashing lights at the end, I interpreted that as him stepping into Sophie's memories and disappearing from the real world. The flashing light sequences that you'll see throughout the film represent Sophie thinking back on the final dance she had with her dad. It's confusing because that's what memories are. She can't see the final dance scene clearly anymore because it's been so long and she no longer remembers it well.