Design a 3D model of a 'skeg had,' a fantastical marine creature. The skeg had should have a streamlined, fish-like body with sleek fins and a long, flowing tail. Its head should feature intricate patterns and scales, with large, expressive, luminescent eyes. Add bioluminescent patterns along its body that glow softly. Ensure detailed texturing and realistic shading to highlight its aquatic and mythical nature.