ultra photorealistic cinematic detailed underwater portrait, a 25 years old sexy mermaid with long deep red hair fully immersed and dynamically suspended in water, her hair spreading widely in all directions with natural buoyancy, individual strands drifting, twisting and flowing in slow motion currents, creating a weightless halo around her head, her expression intense yet softened by a subtle warmth, her eyes reflecting filtered sunlight from above, a gentle positive glow touching her face, silent smile, her skin highly detailed with natural texture, pores and soft imperfections, illuminated by refracted caustic light patterns dancing across her shoulders and collarbone, Strong, warm sunlight breaks through the water's surface, illuminating every detail of her body and face, the diamonds sparkle in the sunlight, she wears a detailed wide oceanic choker with a glittering diamond-studded and leather leash drifting freely in the water, as well as every single green scale on her fish tail, glitter in a brilliant green, gently curving with the movement, her stunning nude upper body has maximal detailed perfect beautiful firm tits, detailed erected nipples, textured and integrated into her form, her powerful fish tail extending downward, covered in fine shimmering scales in deep teal and emerald tones, catching light in soft gradients, the surrounding water filled with floating particles and small air bubbles rising slowly, strong volumetric sunlight beams penetrating the surface above, creating a luminous contrast between bright highlights and deep ocean shadows, the environment vast and immersive with distant rock formations fading into blue depth, shallow depth of field focusing on her face while background softens, cinematic realism, extremely high detail, 35mm film aesthetic, analog film grain, no digital sharpness, atmospheric depth, mystical yet serene mood