Create a stunning, high-quality image showcasing Ariel, the 17-year-old Disney little mermaid, in a captivating full-body pose as she swims gracefully under the sea. The scene is vibrant and detailed with a beautiful underwater background in 16k UHD HDR. Ariel's flowing red hair and shimmering tail are highlighted as she interacts with her aquatic surroundings. Ensure her expression is enchanting and confident, while emphasizing her elegance. Attention to detail in fingers and facial features is important for realism, keeping the portrayal artistic and true to character essence. Avoid any elements like duplicated features, mutations, or artifacts to maintain a polished and cohesive image.