Underwater biomechanical leviathan in a sunken city, ultra realistic, photorealistic, highly detailed, cinematic lighting, vivid colors, atmospheric background, ancient ruins, intricate monster design, mechanical tentacles, glowing bioluminescent parts, detailed textures, dramatic shadows, lifelike expressions, submerged stone buildings, coral-covered structures, marine vegetation, period-appropriate relics, volumetric light beams, dynamic composition, monster in the depths, mechanical parts, detailed underwater scenery, tension and mystery, immersive environment, nuanced lighting, vibrant aquatic environment, architectural intricacies, open ocean, contrast between ancient and futuristic elements, intricate machinery, menacing presence, high resolution, focus on the monster and underwater city