Jean Lafitte's Mermaid Lap Blanket / Sack
The original size of the finished blanket is available for free.
It is meant to be crawled into and measures:
40 inches around at the biggest point.
46 inches long from tip to the beginning of the tail (20 inches from the top till the tail is joined in the round).
57 inches from tip to tail.
For a more tailored “kid version” please follow this link:
A Finnish translation is also available thanks to Lauranieto!
The blanket is knit flat and then joined in the round on circular needles.