Peta from SS gave me the link to a sweet bag. http://www.marthastewart.com/ and search for "sleeper of a bag"
Here it is made up from a 20 cent pillowcase
As you would imagine it wasn't as easy as the instruction makes out. Old pillow cases are not perfectly shaped but it came together nicely in the end and now they will be much easier having done one. These really would be handy to have loaded and ready for the beach for each child.
Here is how mine went together:
Cut in half diagonally
Although the instructions didn't say, I cut off the folded part that stops the pillow falling out. There is a tiny triangle on the other piece too. Sew back up the sides.
I overlocked the long diagonal edges.
Overlapped and pinned in place. This was easier said than done. Due to the case being miss-shapened, I measured the top and the bottom so the sides were parallel to each other. It resulted in a bit needing to be cut off the bottom.
Turned inside out and over-locked across the bottom.
Turn right side out and tie shoulder strap.