I always say that your life depends on your water source,"he said.If you are in a bad situation and have to drink water not fit to drink,you take the risk of drinking wild poisonous water,which can quickly kill you."In this case,a lifestraw will come into play.Finally,Stewart recommends having a raincoat,or anything that can be used to protect you against the weather.Even food should take a back seat to these three necessary items,he says."Everyone gets really worried about food,but the human body is designed to last a long time without food.When it comes to survival necessary items,food'sonthe bottom of the list,"he said.