Buttercream frosting. The Shamu head is RKT covered in royal icing, then fondant. The tail is all fondant. I made the waves by dragging the spatula over and up. After assembling the cake, I sprayed Shamu with cooking spray so that he'd look wet (I only had butter flavor spray, but it still worked fine). There were a few globs of spray here and there, so I used a paper towel to even it out. Very fun cake to make! This was my first time making a RKT form. I found that it wouldn't stay together, so I stuck the mixture back in the microwave for another minute, then really packed it together. It was totally hard when it dried--so not good for eating, but great for working with!