Well, having been newly introduced to the ziploc phenomenon myself, I can tell you I wondered the same thing, but they truly are a must. We stayed in the jungle for several days before coming to Ambergris and everything we had worn while there was soaked. A lot of our clothing was wet from hiking, horse-back riding, and tubing. Being in the rain forest made stuff damp from the high humidity anyway and it never dries out. You can put all the wet stuff in the zip locks so the rest of your stuff stays dry when its time to pack up and go home, or onto your next destination, like us. If you are just going to AC the zip-locks are good for all the wet swimsuits and anything else you wear snorkeling. My only mistake was not bringing more. When I go back to the jungle again, I think I'd pack each outfit in a zip-lock just to save them from dampness.