Dromedary bag
A dromedary bag is a collapsible plastic bladder for holding water for drinking. Backpackers carry dromedary bags in areas where water is not readily available or is not clean enough to drink. Dromedary bags are useful when traveling through the desert, but are generally too heavy for extended trips. The opening sequences of the film Wild demonstrate the heaviness of a backpack laden with water.
Not to be confused with the hydration pack, dromedary bags are able to carry larger amounts of water. They are much more effective at distributing water amongst a group rather than personal use only. The dromedary bag was invented by Sir Thomas Mitchell whilst exploring South east Queensland and seeing Aborigines carrying water in kangaroo skins.