I know that this is really last minute and I am disappointed in myself but I thought I'd share anyway... this is a super easy mermaid, dragon, scaly look I created. Using only fake blood, latex (both from Wilko's), cotton wool and a few eye shadows this looks is surprising easy to create.
I first started off with mixing cotton wool and latex together to create the scales individually. Once I had around 6 scales I started to bond them to my skin using more latex. I made sure the scales curled up slightly to give it more dimension. Once the scales were attached I let them dry then covered them in foundation to match my skin tone. If you are going to use this for a mermaid look you could always paint the scales blue, or green if you are going for the dragon look.
Once the scales matched my skin tone I simply shaded in with black eye shadow and added a ton of fake blood on top of the black, to make it look like the scales were lifted from my skin and all bloody. Its hard to explain but I am sure you can get the gist from the photos. I also added some faint veins and bruising around the scales.
Believe it or not this only took me around 1 hour to create. The longest part was waiting for the latex to dry! It is really easy and super handy if you are in need of a last min halloween costume, but still want to look like you put in loads of effort.