Chocolate Gone Fishing Cake

Name: Chocolate Gone Fishing Cake
Ingredients: 1-1/4 teaspoons baking soda; 1 teaspoon salt; 2/3 cup HERSHEY'S Cocoa; 3 eggs; 2 cups all-purpose flour; 1/4 teaspoon baking powder; 1-1/3 cups water; 1 to 2 cans (16 oz. each) vanilla frosting; Blue and yellow food colors (garnish); Garnishes such as fish-shaped crackers, fish-shaped candies, pull and peel licorice and candy-coated peanut butter pieces (garnish); 3/4 cup (1-1/2 sticks) butter or margarine , softened; 1 teaspoon vanilla extract; 1-2/3 cups sugar