Prepare and bake cake according to package directions, using two greased 9-in. round baking pans. Cool for 10 minutes before removing from pans to wire racks to cool completely.
Spread 1-2/3 cups frosting between layers and over top and sides of cake. Using the back of a spoon, make waves on the top of cake with remaining frosting.
Cut wave shapes out of Fruit Roll-Ups; gently press along bottom of cake. Arrange additional wave shapes and fish candies on top of cake as desired. Tie licorice on one end of candy stick to create a fishing pole.
How-To: To create ocean waves, smooth frosting first. Then use the back of a spoon to make a small twisting motion in one direction. Next, move spoon over slightly and make another twist the opposite way. Repeat. See making ocean waves» Cut the Fruit Roll-Ups in half vertically. Then fold in half, keeping the plastic sides together. Cut into wave shapes. See cutting Fruit Roll-Ups»