This story is Subnautica and Sub: Below Zero based. I include only one species that isn't at all canon to the game which is mermaids/mermen. The story follows A young mermaid that goes by the name of Venus. She's an average everyday creature that follows her own rules and will every now and then break a few. It's thousands of years after the Precursors have disappeared and Alterra has moved on. (Disclaimer: Any of the pictures/videos used through this story are not mine. Including the story cover.)