Told from the alternating perspectives of Bron and Georgie, this book follows their investigations as a tropical idyll turns into a hellish nightmare of wind and water, as secrets from the past and monsters from the present refuse to stay submerged, threatening to destroy them both. The women’s viewpoint chapters are divided by eight ruminations on ways to kill your best friend, as it becomes clear that one of the friends has definitely been thinking of murdering another. The question for us readers is who and why, even as that unidentified narrator mulls over the how .It examines the cost of loyalty, and the choices we make in supporting our friends even when they do wrong. It talks about growing up and growing away from people you once thought the entire world of, and what to do when your worst suspicions of them are confirmed. While this book glories in the joys of swimming, in open water or otherwise, it also has a delicious supernatural element that doesn’t detract at all from the realism of the murder mystery at the core of it. The novel also boasts an ending that I did not see coming, yet was utterly satisfying in its resolution.