Step 1:
The used paper is about 20x30 centimeters and white on the backside.Fold over these two lines, the part in the center is a little wider than the two outer parts.
Glue or tape the edges together.

Step 8:
Make about five small edges

Step 6:
Fold over these two lines.

Step 10:
This fashion doll is about 30 centimeters.

Step 9:
Done.....

Step 5:
Fold over these four lines.

Step 7:
Fold over the curved line and turn the model.

Step 3:
Fold over these two lines

Step 2:
Fold over both lines and turn the model.

Step 4:
Press the edges downwards and the model flat.

DONE! Looks great, right?
This is a video tutorial for folding the mermaid tail by Joost Langeveld: