Create an image of a fantastical underwater world, filled with vibrant coral reefs, schools of exotic fish, and mysterious sea creatures. The scene should be illuminated by rays of sunlight filtering through the water's surface, casting a warm, inviting glow on the entire environment. Add in some elements of magic or mythology, such as mermaids, sea serpents, or sunken treasure. The final result should be a breathtakingly beautiful and immersive image that captures the imagination and transports the viewer to another world.