Create an image of a mystical underwater world where heroic mermaids use their artful abilities to protect an ancient sunken city from danger.

Imagine an enchanting underwater scene, where valiant mermaids, diverse in their descent and gender, utilize their exceptional talents to safeguard the remnants of an ancient submerged metropolis. These mermaids with Caucasian, Hispanic, Black, Middle-Eastern, South Asian, and White ethnic backgrounds have been specially trained in mystical crafts. They swim around spectacular age-old structures with an artful play of light and darkness, creating a haunting yet beautiful ambiance. The city in the background whispers tales of its bygone glory, with grand arches, lost paintings, and ornate statues of forgotten legends. The mermaids are ready to face any imminent danger, ensuring the city remains untouched.