I am coming in late on this, but did get a chuckle from it. I was about to post that no, I didn't want to knit up a shower cap, but I began designing in my head a hat with a large brim, (see Andie Macdowell's big black hat in Four Weddings and a Funeral) for wearing on my head instead of carrying an umbrella, which I do frequently around these parts. Inevitably, the umbrella jostles as I am usually carrying many packages, and falls to one side, getting me very wet.
So I'm disappointed that nobody has yet invented waterproof yarn.