Might as well use a Ziploc bag!
These bags are just like Ziploc bags. In fact, I see no difference. Even the press to seal seam at the top is just like a Ziploc and doesn't appear to be more heavy-duty. Thickness of bag the same too, as far as I can tell. Since I'm not diving with it, I just needed to keep sand/moisture off of items, I could have used a Ziploc and had the same amount of protection. If you truly need a waterproof bag, save your money and buy a thick bag with a heavy-duty closure.