A FoodSaver vac sealer is the best thing I've found for waterproof document storage. This is just a side benefit of owning one, as I use it most for freezing meats (no freezer burn), veggies and fruits. I've even frozen premade pies in them to prolong the storage life. Additionally I use it for vac sealing jars of dehydrated fruits and vegetables, cornmeal and a host of other dry goods. Depending on the accessories you have, it'll marinate meats, prolong the life of produce in the refrigerator and much more.

Seal a change of dry clothes for hiking, camping. Same for first aid supplies and matches.

There's much more, but I won't wear out my welcome with my first post. BTW - disclaimer - I have no association with FoodSaver other than simply being a satisifed customer.

Lee