Salacia: Waga Hakugin no Mermaid

In 2071, North Pole's ice have melted and the land has been submerged. Humanity survived but it's divided into two species: the true humans, those who live in underwater cities, and the Dugons, those who chose to undergo genetic modification to live in the sea. Both species go to war to survive as long as the Dugons consider the humans good to eat...