Ask most people what is inside a camel's hump and they will say water. It is fat. Understanding why that answer is wrong is a good route into how animals survive extreme environments.
Fat, not water
The hump is a store of adipose tissue. Concentrating fat in one place rather than spreading it under the skin means the rest of the body can lose heat freely — insulation only where it is not needed. Respiring that fat does release some water, but the oxygen required for the reaction is breathed in through the nose, and the breathing itself loses more water than the reaction produces. The hump is a food store, not a canteen.
Letting the body temperature drift
Human body temperature is held near 37 degrees Celsius. A dehydrated camel allows its core temperature to fall to about 34 degrees overnight and rise to about 41 during the day.
That drift is the key adaptation. Storing heat in the body instead of sweating it away can save many litres of water per day, and the heat is released passively into the cool night air. It is homeostasis with a deliberately wide tolerance band.
Red blood cells that survive drinking
A camel can lose a quarter of its body mass in water and keep functioning; most mammals collapse well before that. Its red blood cells are oval rather than round and have unusually flexible, strong membranes, so blood stays fluid enough to circulate even when concentrated.
The same membranes matter when the camel finally drinks. A thirsty camel can take in over 100 litres in a few minutes. That flood of water would burst ordinary red blood cells by osmosis; camel cells can swell to more than twice their volume without rupturing.
Everything else is detail worth noticing
Long eyelashes and closable nostrils keep out blowing sand. Broad two-toed feet spread the load on loose ground. Thick chest and knee pads lift the body off scorching sand when the animal rests. The kidneys produce highly concentrated urine and the intestines reclaim water so effectively that the droppings are dry.
None of these adaptations appeared because the camel needed them. Each one is the result of individuals with slightly more useful variation leaving more offspring, over a very long time.