The Nemo cake is made from a 3D egg shaped pan. The fins are made from color flow icing, it does make them one sided, but creates the look you want.
Make the fins ahead of time and do not refrigerate them. I put toothpicks into the color flow icing before it dried to help place and hold it in the cake. The bottom with the turtles is stripped with blue icing colors and brushed around with water to create the E.A.C. from the movie. The turtles are just made with colored chocolate with a candy mold.
Fish was added after transferring to its final destination. Good Luck! It was a lot of fun!