Put all the ingredients in a bowl and stir with a wooden spoon until you get a stiff cake batter.
Grease an 18cm cake tin and line the bottom with baking paper. Spoon in the cake batter.Bake in the oven at 160°c or fan 140°c for 60-80 minutes.
Turn it out and leave it to cool on a wire rack before beginning to decorate it. Melt the marmelade in the microwave and brush it thinly over the top and sides of the cake.
Sprinkle some icing sugar on the work bench. Take enough white icing to cover the whole cake. Add some blue food colour and knead the icing until it is all mixed in. If the colour is too pale, just add a little more food colour.
Roll out the blue icing and cover the cake with it. Trim off the excess icing from around the bottom of the cake.
Wash your hands to get rid of any blue food colour. Add some yellow food colour to some more of the white icing. Knead it again and then form it into the duck shapes.
Use the black writing icing to make dots for the ducks' eyes. Use the green designer icing to pipe the grass on the side of the cake.
Nutritional information is approximate and for the cake only not the icing as I haven't calculated the quantities use.