Another example is when they need to survive the tsunami. They work together because, if not, they would die: first, they climb up the hill togehter, then they find some food and finally, they go back to the beach and start looking for their parents.  

The theme “Desperation makes you take risks”  is one of the themes in way of exploring the novel since it shows was by showing how Kyle and BeeBee are ready to take risks for each other. For example, when Kyle, instead of being safe, goes went out of the room to look for BeeBee. They also take risks when they are so hungry up the hill that when they see a refrigerator, they desperately grab the food as if there is was no tomorrow.
“We hurried to the refrigerator and opened the door. It was no colder inside the appliance than it was outside, but the shelves contained a package of sliced ham, a carton of eggs, a half loaf of bread, a quart of milk, and a jar of dill pickles.”, “We can’t eat the ham,” I said. “The fridge has been off too long; we might get food poisoning. We can’t drink the milk either, but we can eat the bread and the pickles.””
Also Daren is very desperate because instead of listening to Kyle and Bee Bee (they told him to go up hill because it a tsunami could strike) could happen a tsunami, he went goes down to the beach thinking that there he would will be safer because water doesn't burns. He says: “Water won't burn, so the beach is the safest place to be." Yet, going near water is exactly what one shouldn´t do when a tsunami is coming.

the top of the hill.” Later on, Kyle had has to make another important decision because he had has  two options, one was is going uphill, and the other one was is  going to the beach, but he remembered remembers what he read on the Tsunami sign in the morning and they went go up hill.

That This quote shows that they never give up even though they are exhausted.