the tanks are a great place to test out small containers to see just how WP they are..no joke.a bit of string attached to keep them from getting into the "works" and left alone for a few weeks and you will get a good idea of just "waterproof"a match case is.i have done that with things like pill bottles and urine sample jars that i was thinking about using for wood matches.all that motion from filling and emptying dunks the test object around to give it a real test.left alone for a week or two should do it.