Thank you so much! I made the fins by cutting a cardboard shape of each fin and wrapping it in paper mache. After that dries, I sand papered it down for smoothness, painted Gesso on for more smoothness, and then when that dried I painted the colors with acrylic paints. However, for the arm fins, before I paper mached, I glued tiny strips of cardboard in the center of each fin spike to give it the ribbed look. Hope it helps!