Or a possible alternate container, a waterproof plastic medicine bottle.

Actually, I don't carry a 'ditch kit', never have, and I don't plan to start. The most important quality is between the ears, experience & judgement. It works like this: if conditions are too dangerous to be on the water, I am off the water. I do keep important items in my daypack, and it is within easy reach, so if I had to ditch, I would grab it.

Now back to original topic...