Richard Ferguson wrote in
:

Expand a little on this bivy bag. The bivy bags that I am familar with
are usually made of goretex, and go over one's sleeping bag, or body if
you do not have a sleeping bag with you. What you describes sounds
very different. Is it just a large orange plastic bag?

I forgot to mention in the previous post. The primary advantage of the
orange survival bag to the kind of bivy bag you're talking about is that the
former is small enough that you can put it in a pocket in your PFD. If
you've got a fancy gortex bivy bag it would likely be packed in with your
sleeping bag which won't help if you capsize and become separated from your
boat. When considering safety gear think of what you would need if you
became separated from your boat and carry it in your PFD.