Ancient Artifact in an Underwater Cave

Photorealistic undersea cave scene featuring an ancient artifact. A weathered bronze tablet partially buried in fine sand rests on a slick rock ledge, covered in sea-worn patina and encrusted with coral. Intricate engravings and a central emblem are visible, catching mineral glints as light filters through the water. Sunlight pierces from above, casting shimmering caustics on stalactites, stalagmites, and the artifact. The water is crystal-clear with suspended particles, blue-green hues, and slow-moving bubbles. Surrounding walls are rough and encrusted with algae; tiny fish weave through the shafts of the cave. The scene should be hyperrealistic with 8k resolution, high dynamic range, macro focus on the artifact, shallow depth of field, and natural-looking color grading. Mood: ancient mystery and exploration; consider including a distant diver silhouette for scale.