The sea sisters / Lucy Clarke.

Also published as 'Swimming at night"

Sisters Katie and Mia have a strained relationship and Katie is almost relieved when Mia embarks on an around-the-world trip with her best friend, Finn. Then, one devastating night, Katie is told the news that Mia is dead - and the police say it was suicide... When Mia's things arrive back from the other side of the world, Katie clings desperately to Mia's journal as the only remaining part of her sister. Distraught that the last conversation they'd had was an argument, and refusing to believe that Mia would take her own life, Katie leaves behind her orderly, sheltered life and, with only the entries of Mia's tattered journal as her guide, sets out on a journey to find the truth...

Adult.