On a world covered entirely by a boundless ocean, generations of humans have eked out a precarious existence atop huge floating plants, crafting a rich but insular culture shaped by scarcity, superstition and the constant danger of the sea; when a bold individual investigates the origin of lethal, tentacled predators and the hidden truths behind longstanding taboos, he comes into conflict with conservative leaders and rival groups, forcing his community to confront uncomfortable realities and adapt creatively to secure a safer, more sustainable future.