The Mermaid and the Treasure of the Bay by A. Algeri

"The Mermaid and the treasure of the Bay" is the first adventure of Brinn, a young woman who had recently returned to her homeland, Nyar Kaad, after years of being away.
For her mother and sister it’s only supposed to be an episodic stay, because their intention is to return to the capital, Adaria, held by both aristocrats, by then, to be their home. Brinn, however, isn’t interested in living in the golden cage of high society and aspires to a different existence, that will push her to oppose the decisions of her family and to pursue a destiny according to her own wishes.
The accidental discovery of what looks like a map to hidden treasure, buried in Nyar Kaad, according to tradition, by pirates once dwelling in the settlement, will push her to search for the hidden riches- an undertaking that the protagonist will face courageously, at the cost of challenging her fears, the rigid social conventions, and more literal dangers to her person, venturing on a journey into the local legends and the past of her own family, until reaching an unexpected epilogue.
Set to Isara, a fantasy world inspired by the period between the seventeenth and the first decades of the nineteenth centuries, "The Mermaid and the treasure of the Bay" is a journey full of mystery in the universe where real and supernatural coexist intersecting in a subtle and insidious way, a world divided between palaces and largely unexplored expanses, an opulent capital and boundless oceans.