Jellyfish floating in dark water tank. Translucent body, iridescent and ethereal. Glowing network of veins and arteries within tentacles, glowing with bioluminescent effect (vibrant blues and purples). Dramatic lighting from above, creating stark contrast against pitch-black background. Beams of light cutting through water, illuminating particles. Ultra-high detail, photorealistic rendering. Underwater caustics visible. Cinematic color grading emphasizing the glow of tentacles against the darkness.