Siwash anchor

The April issue of SK had a letter from a reader making reference to a Siwash anchor in the March issue. I can’t find any info on the internet. Can anyone describe what a Siwash anchor is? Thanks.

It’s a mesh bag
Fill it with whatever heavy stuff you find whbn you land, and use it to moor your boat just off the shore so it doesn’t bang on the rocks.

Check the back issue’s of SK. there’s a how to artical about three issues ago. Feb 08 I think