First I took some old T-shirts and cut them into the skirt with a tail - this is the underpart which no one sees anyway. Then I chose my scale fabrics, and cut scalloped strips out of them.
I then pinned on the scallops and sewed them down along the bottom/scalloped edge. I just built the scales in the same process all the way up the skirt.
Hind sight being 20/20 of course, it probably would have been faster to fuse the scales, but then again, maybe not.
Any way, a happy mermaid.
As Mr. Riley says, probably the first girl who ever wanted to dress up like a quilt.