wow you can tell these guys never go fishing offshore. LOL
If you get it at a ice house it will come wrapped in brown butcher like paper. Just leave it in the paper, then no burns. Walmart sells it and most stores sell it near the coasts. It's hard to say how it's packaged but wrap it in newspaper if it isnt in paper.
It will last 3 - 5 or 6 days depending on the cooler and how many times you are in and out of it. I usually throw 2 or 3 blocks in a 80 qt. cooler and load it up with regular ice on top. I use the dry ice to keep the regular ice frozen and use the regular ice in the other coolers as needed.