'On the Eighth Day' by Felicity Goodall

The survivors take to the sea. Centuries of walking darkened streets in fear have remodelled female lungs, prepared them for evolution. Those sharp gasps before flight have taught them how to breathe. Not underwater, not at first, instead they surface like whales, gulping oxygen, before diving deep to hide. Sharp teeth evolve as hunted become hunters. Armoured skins grow thick as sharks, and, like their fishy sisters, backs darken to better hide from surface predators - the men in boats who have also taken to the swelling sea but have no kinship with her.

The ocean births a new age, the Gynaecene .

Ocean-going females swim in packs to hunt for mates. Captives are put to work to judge their worth: as jellyfish-herders, shepherding the colonies to purify the sea; collecting coral fragments to replant; and finally dam-breaking, dangerous work to restore the free-flow of rivers, allowing fish to visit ancient spawning grounds, tempting the naiads to return.
 
In this new world of sea caves and kelp forests, imaginations are ignited but without paper, without libraries, each woman becomes a book, communicated in dance, mime and with practice, telepathy.

Herstory - sisters memorise the past and read a disturbing pattern in this new age, a contorted replication of the Anthropocene. How can we do better? they say.
A boy is born with a brood pouch. On maturity, he too is mated, carries another and to their surprise nurtures him.

Shark-skins are shed as the sisters learn a new dance, drum new rhythms to spread the word of this evolution. They rise to the surface through glittering shoals, break into clean air to sing their tale with voices they had thought silenced.

The boats of men are gone, the land is green, the naiads have returned.

Earth-daughters hold their breath.