They were tired.
All the exploitation and warmongering nature of men exhausted them. It seemed men will never change, alter their nature. They will just wipe each other and the rest of the world out with them.
So they decided they will create a world of their own, without men.
A group of them isolated themselves in an island in middle of nowhere and started to worship Mother Goddess Kali; decades passed by before the goddess was pleased and she appeared before them.
She granted them their wish and a boon.
Thus the island was formed.
She blessed them that only women and men who respected them as equals and shared their views of a peaceful life will be able to put their feet in that island, to others that island will be invisible, they will be able to walk through it without seeing it.
And she blessed that if men outside their small world succeed into killing each other they won’t be able to destroy the earth and other inhabitants of earth.
So while the world around them squabbled and fought they lived a peaceful life.
Those pure-minded souls that could see them told about them to others, and when greedy people tried to win that island filled with gorgeous women they saw nothing. Only blue ocean greeted them.
Thus started the stories of mermaids and sirens; gorgeous phantom women who misguided sailors. Everyone talked about their beauty, lusted after them but never touched one.
Once in a while a pure-hearted soul left the remaining world behind and joined them, the stories got greater wind behind their sail.
Their world thrived under the veil of mysterious armour.
One sad day they realized that human beings have destroyed the rest of the human population. They stepped out of their invisible island to make the earth habitable again.