Song of the Sea is a small DLC-sized mod for The Elder Scrolls 5: Skyrim, adding new siren-themed quests, abilities, and locations. Engage in an immersive, character-driven storyline, gain the ability to become a siren, acquire powerful new water-based powers, and even live in a completely underwater player home in the Sea of Ghosts.
I managed to create a functioning proof-of-concept set of siren-adapted armor. Vanilla armors won't work on mermaid characters because the armor meshes have legs. However, I have figured out how to remove them and allow an adapted armor to be overlaid on top of any siren body. This means they will natively work with any of the additional tail models we plan to add without any modification. Siren-adapted armors will have reduced weight and armor rating due to their reduced coverage, though this can be negated somewhat via the "hardened scales" perk from the siren skill tree.
I plan to create adapted versions of most of the standard vanilla armors, such as leather, ebony, steel, glass, stalhrim, daedric, etc. but decided to start with the Ancient Falmer set as it is the most siren-like in appearance in my opinion.