On such a full sea - Chang-Rae Lee

Lithe and tiny, Fan is a diver at the New China settlement of B-Mor, a worker colony long-ago known as Baltimore, her circumscribed world the temperature-controlled fish tanks that feed a contaminated continent, and Reg, the golden-skinned, simple-hearted man she loves.

Rigorously pressurised and demarcated, the dystopian America Fan serves is ruled by the professional Charter caste. While B-Mors are obedient and tranquillised by duty and the fear of chaos, the pampered, ruthless Charters inhabit idyllic, over-supplied communities behind whose gates they jostle ceaselessly for dominance. Estranged from nature, B-Mors and Charters alike shy from the spaces between, where 'counties' people - outcasts, free-thinkers and renegades, bandits and pedlars - forage and grub and steal and kill.
One quiet day Reg is removed from the colony - whether for a nameless infraction, or because he is disease-resistant in a world where no one is C-free, it is impossible to say. Fan decides she must follow.
But her departure threatens to disrupt the whole order of B-Mor society, and only savage action can hold it together.

A mesmerising narrative of courage and longing, On Such a Full Sea is an epic tale: brilliantly speculative, absolutely involving and profoundly humane.