A diverse group of dedicated local pool members who narrate the opening section of the novel in a collective voice. They use daily laps to cope with the frustrations, trauma, and chaos of their aboveground lives. Though they possess vastly different careers and personalities outside the water, they unite through strict observance of unwritten pool rules and communal rituals.

A retired lab technician and dedicated swimmer currently experiencing the early stages of frontotemporal dementia. She is a Japanese American woman who spent part of her childhood in a World War II detention camp in the desert. Alice is known for her impeccable style, flawless makeup, and fierce devotion to her family.

An author who documents her mother's life in an effort to honor her memory. She has physical compulsions, such as tapping doors three times and clicking her teeth, stemming from childhood anxiety. As an adult, she maintains physical and emotional distance from her mother, a choice that causes intense regret when she begins to recognize the warning signs of Alice's illness.

A Japanese man shaped by wartime experiences that dictate his severe dislike for pumpkins. He maintains a quiet devotion to his wife, setting out two fortune cookies every evening to celebrate their time together. He relies heavily on denial as a coping mechanism, acting as though Alice will soon return home once she is placed in care.

A for-profit memory care residence personified with a cold, corporate, and controlling narrative voice. It presents a luxurious facade in its lobby to attract wealthy families while subjecting its residents to neglect and constant surveillance. The facility views patients purely as commodities and prioritizes shareholder profits over genuine medical care.

A man from Alice's youth with whom she shared a profound romance. Their relationship ends suddenly when he joins the Air Force and falls in love with someone else. Alice keeps his letters in a drawer by her bed for many years.

A stoic woman incarcerated alongside her children in a desert detention camp during World War II. She instructed Alice never to let anyone see her cry. She later lives to be 101 years old, receiving dedicated daily care from her daughter.

A man arrested by the FBI at the start of World War II and separated from his family until the conflict ends. The trauma of his incarceration changes him profoundly, ultimately causing him to abandon his family entirely.

Alice's firstborn child who possessed an unusual heart. She passes away shortly after birth, and her body is donated for scientific study, a decision Alice later deeply regrets.

The manager of the underground pool facility. He serves as the primary communicator between the worried swimmers and the various structural experts investigating the mysterious cracks forming on the pool floor.

The staff member responsible for monitoring the underground pool. He enforces safety measures and eventually blows his whistle to signal the final closure of the facility.

A regular patron at the underground pool. He maintains a firmly positive outlook regarding the structural issues, attempting to find a silver lining in the face of the community's anxiety.

A depressed member of the pool community. She expresses a fatalistic view of the pool's structural damage, declaring that everything in life amounts to loss.