Craft an enchanting masterpiece featuring a mythical creature that combines the grace of a mermaid with the beauty of a unicorn. Picture a majestic being with the upper body of a captivating mermaid, her shimmering scales glistening in the gentle light, seamlessly transitioning into the sleek, elegant body of a unicorn below the waist. The unicorn's coat is pure white, adorned with iridescent swirls that mimic the patterns of seashells, while a magnificent horn spirals elegantly from its forehead, emanating a soft, ethereal glow. Delicate fins extend from its forelegs, shimmering with hints of silver and gold, as it stands proudly amidst a tranquil, underwater realm filled with colorful coral and swaying seaweed. The mermaid unicorn's eyes, a mesmerizing blend of deep sea blues and mystical purples, exude a sense of magic and wonder, captivating all who behold its beauty.