A vibrant 4K anime wallpaper depicting a fantastical underwater city illuminated by bioluminescent sea creatures. The scene showcases elegant coral structures resembling ancient architecture, with colorful fish swimming gracefully among them. Glowing jellyfish drift through the water, casting a soft light on the vibrant marine life below. In the foreground, a group of merfolk playfully interacts with dolphins, while schools of shimmering fish create a mesmerizing dance around them. The overall atmosphere is magical and serene, evoking a sense of wonder and adventure in this enchanting underwater realm