What are the symbols in Dry by Neal and Jarrod Shusterman?

There are plenty of symbols that exist in Dry. One symbol that is persistent throughout the story is a gun. Symbolically, Shusterman isn't breaking new ground with firearms being symbolically significant.
The guns in the story have a traditional duality to them. On one hand, they are symbolic of extreme violence. We see this in the first part of the book when the water truck is trying to deliver water to the power plant, and readers are told that the guy riding "shotgun" is actually armed with a shotgun. The detail foreshadows that trouble is coming for the pair. The mob crowd outside sees the gun and actually uses it against the man.
Even Alyssa sees firearms as pure evil in the beginning of the story. She is so adamant that guns are bad that she refuses to give Kelton the clip to his pistol. As the story progresses, readers see Alyssa's opinion of guns change. After her scary encounter with a fake convenience store clerk, she makes sure that Kelton does indeed know how to handle the pistol. Then she hands him the weapon's magazine. Alyssa now sees the weapon as a necessary tool for protection and survival.
Another symbol in the book is Kelton's canteen. It is a symbol of hope, friendship, and even love. Kelton will repeatedly pull his canteen out and let Alyssa have sips from it. He knows that the action will anger his dad, but he does it anyway in order to help a fellow human in need; although he does have selfish reasons. He really likes Alyssa and is hoping to win her affection, but that canteen and his offers repeatedly give Alyssa the life-saving water that she needs.