Many of my daughter's friends had just had princess cakes, so I really wanted to do something different for her fourth birthday. Not sure where I got the original Mermaid Birthday Cake Design from, but I looked through all the mermaids on this site to collect ideas for what I had in mind - thanks for the resource!
I actually put the mermaid together a couple of weeks in advance, as having a busy family, couldn't afford to leave it till the last minute. Just bagged her up & hid her in the back of the fridge.
I tapped her legs together tightly first. Her tail is actually the berry-flavoured roll-ups. They are conveniently different shades, which I liked the look of. I used a scalloped shaped ruler (scrapbook ruler actually!) & a sharp knife to cut the roll-ups. I found it easier to put the roll-ups flat in the fridge first, so they weren't too sticky whilst cutting, but by the time I had finished cutting, they had softened enough to wrap around her legs. The actual fin was a thin piece of card, wrapped in roll-ups.
I started at the bottom, to get the layered look. For the life of me, I couldn't find appropriate swimmers for the doll, so I just used a piece of ribbon & decorated with hot-fix rhinestones.
I did have a Dolly Varden tin, which did make it easier. The cake was a butter cake (a recipe I found on-line, which was large enough for the tin). I hollowed out a small section, so the doll would be sitting on the rock, without looking like she was perched precariously on top. I did use a couple of toothpicks to help keep her in place. I then used that hollowed out section for an additional rock at the bottom of the island for the candles. The frosting was chocolate & I swirled it on for the rougher `rock' effect. It is surrounded by blue jelly, with little icing fish, crabs, turtles etc. These were purchased from my local cake store.
This was actually a really easy cake, with great effect. She was an absolute hit, though people didn't believe that I made the tail myself!