For those of you preparing your bags (BOB, GHB, Hunting, etc) . . . . If you're a hunter, hiker or just a prepper you know how annoying water can be (rain, snow, or falling in a creek) on the contents you keep in your pack. I've got a solution to offer that I've been using for hunting and its been working pretty well.
For the gear I need daily access to I keep in good quality zip-lock bags, for other items that I only need when I need it and not very often, I seal it in a bag with my vacuum sealer before I leave.
This has proven helpful even for items that can get wet but increase in weight when they do (ie mule tape for building shelter or hanging my elk quarters in a tree). I have also found it helpful in extending life to the items in my IFAK because the packaging some of the items come in get wear holes pretty easy. Also items such as my lighters that evaporate their fuel, vacuum sealing seems to extend their life a bit, including keeping my tinder dry.
Another advantage is that the vacuum sealing process shrinks their size down to pack much smaller in the pack