Beach find

After all the storms there is an awful lot of debris up on the beaches.  Mostly plastic and pieces of rope, but today I came across this.  I unrolled it to find it what it was, but was still none the wiser.  See extra.  

Spoke to a neighbour who is a diver and she told me it's a flotation device so folk know where you are when you are, for example, wreck diving.  

I thought is looked like a small body bag, and was relieved to know it wasn't!