A surrealist digital illustration of a massive, crab-like mechanical submarine walking across the dark ocean floor. The exterior is weathered copper and brass, but glowing yellow windows reveal a lush, botanical interior with hanging plants and libraries. Bubbles rise from the mechanical joints. The surrounding water is filled with glowing blue jellyfish and neon coral. High contrast between the dark, cold abyss and the golden, inviting interior. Painterly texture, concept art for a fantasy film, intricate mechanical and organic details.