The story has a really strong and intriguing premise with a case of mirror twins which is unique in itself. The small details that the author has included that are just slightly wrong or out of place are a great tool to use to build a sense of foreboding. The underlying notes of jealousy and feeling as though you are out of place in your own life is clear from the start. We have an unreliable narrator and a difficult situation, add in the sailing asprct and you have yet another unique factor for this story.