You hit the nail on the head by assuming it was water that caused it. My boat has no dry stroage and I've lost some myself to water damage. The last time that happened i picked up a worm binder with the zip style plastic bags in it. Left my grubs in their original package and put (2) packs of grubs per bag in the binder. Three years later and i've not lost any more to water damage. I was actually pretty shocked how much that little binder held(at least as much as the same size boxes in your pic).