post-apocalyptic scene, Tsar Fish, mutated giant catfish, protagonist in combat gear, aiming rifle, decrepit metro tunnel, submerged ruins, murky water, algae-covered walls, dim lighting, flashlight beam, gas mask, distressed textures, rusted metal, dripping water, tense atmosphere, action pose, environmental storytelling, 3/4 view, atmospheric perspective, dynamic composition, high contrast lighting, survival theme, gritty realism.