The future is flooded, the fall of human civilisation partnering the risen sea level. Taking to the oceans to survive, a bio-engineered remnant of Man lives a primitive, yet harmonious, life undersea in the tropics. But the Cetari are not alone in staking a claim to sapience on drowned Planet Earth. Challenging them is the numerically superior Piawro, a race of humanoidal amphibians jealous of the prosperous Merfolk.