Jay is a 17-year-old boy burdened by profound guilt and the traumatizing legacy of his father's harsh upbringing. Estranged from his family for two years after fleeing his abusive home, he undertakes a desperate and irrational solo dive into the treacherous waters of Monastery Bay to recover his late father's remains. He hopes this act will earn him redemption in the eyes of his family and the local diving community.

Mitt is a local diving legend in Monterey whose public persona masks a volatile, abusive reality at home. A man deeply disillusioned with modern society and commercialism, he possesses encyclopedic marine knowledge but forces it upon his son through cruel, relentless drills. He struggles with alcohol addiction and terminal cancer before taking his own life, leaving a massive psychological shadow over his family.

A massive, scarred, and ancient marine predator moving through the deep waters of Monterey Bay. Solitary by nature, the old whale bears the physical marks of past battles and propeller strikes. Operating entirely on instinct and the amoral rules of the deep sea, its immense scale and power embody the terrifying indifference of the natural world.

Hewey is a former dentist and Mitt's only true friend in the local community. Despite being deeply embedded in a diving community, he notably cannot swim. He acts as a crucial, compassionate mentor figure for Jay, often softening the blows of Mitt's cruelty and offering philosophical, merciful perspectives on life and tragedy.

Zara is Jay's mother, a woman who tries to hold her fractured family together despite her husband's erratic behavior and eventual terminal illness. She desperately wishes for Jay to return home and reconcile with his father, making emotional pleas that weigh heavily on Jay's conscience.

Nan is Jay's older sister and a speech pathologist. Growing up in the Gardiner household, she developed a protective shell and a distinct confidence. She is deeply frustrated by Jay's long absence during their father's terminal illness and desperately tries to contact him to force a family reconciliation.

Eva is Jay's other older sister, studying chemical engineering. Like Nan, she is angered by Jay's estrangement but possesses practical, scientific knowledge that leaves a lasting impression on her younger brother. She joins the family's coordinated efforts to convince Jay to visit their dying father.

Chloe is a friend of Jay's whose family took him in after he ran away from his abusive home. She provides him with a temporary sanctuary and some of the secondhand equipment he uses for his dangerous dive at Monastery Beach.