Melancholic mermaid on ancient stone in underwater forest

An ethereal mermaid with bioluminescent scales and flowing, seaweed-like hair, sits on a moss-covered ancient stone in a deep, underwater enchanted forest. Moonlight filters through the waters above, casting ethereal beams on the mystical flora and fauna. The scene evokes a sense of melancholy beauty, captured in a photorealistic style with a touch of dark fantasy horror.