Under the Sea Tiered Cake

Mermaid tail scales, mini clams and ruffled wave-effect icing stack up to marvellous marine effect in this double-decker bake. Whatever kind of sponge sits under the trimmings (probably better not follow the theme as far as making it fish-flavoured!), this is one centrepiece that’s really dressed to impress.
Made using Renshaw Ready to Roll White Icing, Wilton® Colour Right System  and the Small Easy Rose Cutter Set


To make the coloured icing to decorate our bake, we added the stated amount of Wilton® Colour Right System icing colourings to Renshaw Ready to Roll White Icing. (Please note: you’ll need a total of 2.6kg icing to make this recipe.)

To cover the cake board

  • 300g Renshaw Ready to Roll White Icing
  • 1 tsp Tylo powder

To cover both cakes

  • 1.5kg Renshaw Ready to Roll White Icing

For blue waves on bottom tier

  • 250g blue icing (5 drops Blue, 2½ drops Brown)
  • 150g white icing
  • 1 tsp Tylo powder

For fish scales on top tier

  • 100g light pink icing (end of cocktail stick dipped in Red)
  • 100g dark pink icing (2 drops Red)
  • 100g jade green icing (2 drops Blue, 1 drop Yellow – mixed in a small pot with most, not all of the colouring added to the icing)
  • 100g lilac icing (3 drops Red, 1 drop Blue – mixed in a small pot with only a quarter added to the icing)
  • Under the Sea Sprinkletti Mix or Unicorn Sprinkletti Mix
  • Silver Edible Glitter Dust (optional)

For the clamshell

  • 1 egg white, weighed (approx. 35g)
  • Caster sugar, twice the weight of the egg white (approx. 70g)
  • Silver Edible Glitter Dust


  1. A day or two before your undersea party, prepare the cake board. Mix 300g of Ready to Roll White Icing with 1 tsp of Tylo powder, roll out and cover a 12″ round cake board. Leave for the icing to harden.
  2. Make the cake sponges to a recipe of your choice – you will need one 8″ cake and one 6″ cake, both about 12cm high.
  3. Roll out Ready to Roll White Icing and cover both cake tiers separately.
  4. To make the ‘waves’ on the bottom tier, take the blue icing and the white icing and divide to make 4 ombre shades, from palest to darkest, as follows:
    25g blue + 75g white (palest)
    50g blue + 50g white 
    75g blue + 25g white
    100g blue (darkest)
  5. Knead the blue and white icings together so you have 4 balls of varying shades of blue. To each ball add ¼ tsp of Tylo powder and knead in well until the icing feels elastic.
  6. Starting with the palest blue coloured icing, shape into a sausage 10cm long. Roll the sausage out into a long thin strip approx. 50cm long and 7-8cm wide – the addition of the Tylo powder means that the icing will have strength and elasticity so you can roll it out thinly (approx. 2mm) and it will be more resistant to tearing when you handle it.
  7. Using a pizza wheel, trim a straight edge on one side of your strip and cut the other edge in a random wavy line.
  8. Dip a clean decorating brush into cooled boiled water and paint a ring of water 5cm down from the top of the 8″ cake.
  9. Wrap the strip around the cake, pressing along the bottom straight edge to secure it to the cake. Use your fingertips to gently roll the top, wavy edge of the strip outwards and downwards to give it shape.
  10. Repeat steps 6 and 7 for the next palest shade of blue icing, then use water to attach this to your cake about 2.5cm below the palest strip. Repeat for the third strip. With the last strip, ensure that the straight edge is around the very base of the cake, touching the cake board.
  11. Separate out some large blue pearls from the Unicorn Sprinkletti Mix, or some white pearls from the Under the Sea Sprinkletti Mix, and stick to the waves with a little edible glue.
  12. For the scales on the top tier, roll out each of the 4 colours of icing (light pink, dark pink, jade green and lilac) until 2mm thick.
  13. Use the larger cutter from the Small Easy Rose Cutter Set to cut out lots of icing shapes. Cut the shapes in half lengthways using the pizza wheel and divide the strips into ‘scales’ of pairs and trios.
  14. Starting at the bottom of the 6″ cake, wrap a 1cm strip of (any) coloured icing around the base of the cake – this will help to hide the join between the tiers.
  15. Brush the back of each ‘scale’ with water as you attach them to the cake, starting at the base and completing one layer around the circumference of the cake before moving upwards to the next layer. Ensure that you stagger and overlap the rows so that there are no gaps showing.
  16. Continue working your way up the cake and over the top edge, then cover the top of the cake with concentric circles of the scales. If desired, finish with a spray of silver edible glitter dust. Carefully place this top tier on top of the bottom tier.
  17. To make the clamshell on top of the cake, whisk up the egg white until it forms stiff peaks. With the whisk still going, add the sugar a teaspoon at a time until it is all incorporated and the meringue mix is thick and glossy. Use a cocktail stick dipped in the Wilton blue icing colour to tint the meringue a delicate shade of pale blue.
  18. Line a baking sheet with baking parchment. Put the meringue into a disposable piping bag and cut off the end to make a hole approx. 1cm across.
  19. Pipe two clamshell shapes approx. 10 x 10cm – pipe one central straight line, tapering it towards the bottom, then pipe three lines on either side of this, also tapering and gradually getting shorter in a fan shape.
  20. Put the meringues in the oven at a low heat (about 80˚C) to dry out for 2 hours or overnight. Leave in the oven to go cold.
  21. Sandwich the clamshells together with 2 tablespoons of buttercream and add a large pea-sized ball of fondant icing for the pearl. Spray with silver glitter dust and attach to the top of the cake with a blob of royal icing.