Todd is a 57-year-old American billionaire who built his immense wealth by developing the highly addictive social media and gaming platform "Playground." After receiving a diagnosis of Lewy body dementia, he attempts to preserve his fading memories by dictating his life history to a black monolith AI device. Raised in Chicago by a highly competitive father, Todd approaches both technology and personal interactions as a series of strategic games to be won.

Rafi is a brilliant African American scholar originally from a poor Chicago neighborhood. Driven by his father's intense demands to academically out-compete his white peers, Rafi develops a formidable intellect and a deep love for literature. He carries an immense burden of irrational guilt over his parents' separation and his sister's tragic death. As an adult, he lives quietly on the French Polynesian island of Makatea, working as an assistant schoolteacher.

Ina is a sculptor of French Polynesian descent who spent her youth moving constantly between military bases. This itinerant upbringing leaves her with a persistent sense of cultural dislocation until she forms a tight-knit trio with Rafi and Todd at college. Currently living on Makatea, she channels her artistic impulses into creating a massive sculpture out of plastic debris that washes ashore.

Evelyne is a renowned French Canadian oceanologist who feels truly comfortable only underwater. Having faced down the sexism of mid-century oceanography, she became one of the world's foremost advocates for marine conservation. Now 90 years old, she lives on Makatea, where she continues to dive daily among the manta rays while plotting her final book.

Didier is the reluctant mayor of Makatea. A former local soccer hero whose sports career ended due to injury, he has zero interest in politics but accepts the mayoral burden after the previous leader's death. He currently guides his small community through a monumental referendum regarding a massive seasteading project that promises wealth but threatens environmental ruin.

Bart is a quiet, accommodating academic who falls in love with Evelyne during their college years. Understanding early on that his wife belongs to the ocean, he willingly takes on the primary responsibility of managing their home and raising their children while she embarks on lengthy research expeditions.

Donald is Rafi's father. Feeling profoundly mistreated by a racist society, he channels his frustration into intensely drilling his son on advanced reading and academics. He demands that Rafi become smarter and faster than his white peers as a form of personal revenge against a world he feels has wronged him.

Michael is Todd's father, a stockbroker who thrives on combat and competition. He intentionally instills a ruthless, strategic mindset in his son by drilling him in complex board games. His self-destructive tendencies and secretive financial practices leave his family in poverty after his sudden death in a car accident.

Known universally as the "Queen" of Makatea, Palila is a respected community elder. Having survived radiation sickness from French atomic bomb tests earlier in her life, she now acts as a vital cultural historian for the island, using her vast repertoire of songs to record the community's past.

Sondra is Rafi's younger sister. While Rafi spends hours away studying, they share a special, protective bond at home. She is fiercely loyal to her brother and completely willing to stand up to threatening adults in order to defend his intelligence and well-being.

Wai is a local Makatean guide whom Evelyne considers the best human navigator in the world. He possesses an uncanny ability to read the ocean currents and frequently accompanies the elderly oceanographer to ensure her physical safety during deep dives.

Kinipela is Wai's young daughter, an inquisitive Makatean girl who quickly becomes enraptured with the underwater world. She serves as a protégé to Evelyne, absorbing the scientist's vast knowledge of marine biology and carrying on the legacy of ocean conservation.

Wen Lai is the polyglot owner of the "Chinese Store" on Makatea, providing the isolated island with essential commercial goods. A student of philosophy and a respected elder, he provides the black and white Go stones that the residents use to cast their votes in the island's critical referendum.

Profunda is an advanced AI machine provided by the US consortium to educate the people of Makatea about the proposed floating city. It delivers remarkably transparent and honest answers to the islanders' relentless questions, inadvertently validating their environmental concerns.

Emile is a French Canadian inventor and a colleague of Jacques Cousteau who helps develop early SCUBA technology. By testing his breathing inventions on his adolescent daughter, he inadvertently sparks her lifelong obsession with the underwater world.

Roti is Didier's wife. After medical struggles to conceive a child led her to lose interest in physical intimacy, she approaches their marriage with pragmatism, allowing her husband to fulfill his needs elsewhere while continuing to offer him vital grounding advice on his mayoral duties.

Afa is an adopted Makatean boy raised by Rafi and Ina. Known affectionately as a "crab boy" for his constant beachcombing habits, he and his sister represent the couple's quiet, integrated life on the island following the tragic death of the children's biological parents.

Hariti is the adopted Makatean daughter of Rafi and Ina, described affectionately as a "timid dancer." Her discovery of a plastic-filled seabird directly prompts her mother to begin assembling a massive environmental art sculpture in their yard.

Danny is the twin son of Evelyne and Bart. Raised primarily by his father while his mother travels the globe for oceanographic research, his personality diverges sharply from his twin sister's as they grow up entirely on dry land.

Dora is the twin daughter of Evelyne and Bart. She spends her formative years growing up in the United States under her father's primary care, learning to accept her mother's frequent, months-long absences for deep-sea diving expeditions.

Jules is the deceased former mayor of Makatea. A highly capable leader, the local community assumed he would guide the island indefinitely before his passing forced a reluctant Didier into the mayoral office.

Hone is the son of the former mayor, Jules Amaru. A former soccer rival of Didier's, he currently runs a climbing outfitter business on Makatea and takes a markedly relaxed view toward the American consortium's proposed corporate investments.

Manutahi is a technically minded resident of Makatea who maintains the island's solar energy infrastructure. His work directly represents the island's gradual shift back toward natural sustainability following the highly destructive phosphate mining era.

Widow Poretu is a local woman on Makatea who carries on a quiet affair with the island's mayor, Didier Turi. The relationship exists with the tacit permission of Didier's wife, offering him an emotional release from his stressful duties.

Tamatoa is a remote hermit living on Makatea who deeply dislikes outsiders. Palila is the only person on the island with whom he will readily communicate, prompting the mayor to ask her to personally invite him to the vital community referendum.