The Sealskin

Cedric's lived his entire life with the same close-knit group of people. He's taken care of his older sister, grandfather, and slightly insane mother with no father to help him. But when he starts to piece things like a shark attack, a new girl, and an old man with a young man's strength, together his family is murdered.
Demanding answers and revenge, Cedric unknowingly dives into a new world full of selkies, kelpies, merfolk, and a dangerous plot that only he, Taylor, a girl he's known since birth, and Joan, a girl he met a week prior to his family's murder, can uncover.