Water, with out it you are screwed the 3 3rules. 3 minutes with out air, 3 days without water,
3 weeks without food, in a country like Africa & Australia no water & the sun will kill you, with shade & water you should last 2 weeks . The Australian Army ran very good survival courses all the other stuff is good but no fluid & you are dead. There is a drinking straw called life Straw it filters dirty water enough for you to drink, if you get sick on contaminated water chances are it will kill you. water purification tablets are a must , know what bush fruit & plants you can eat some are poison & if in a vehicle do not leave it, a personal emergency location beacon is a good idea.