Your bladder and kidneys need water to function. Initially, your kidneys slow sending water to your bladder which is why your pee turns dark. Then you start losing water in your blood to keep organs functioning but the decrease in blood volume causes your blood pressure to drop. This makes pumping blood increasingly difficult for your heart so your body will start sending less blood to your organs. This starts damaging all your organs and eventually your kidneys stop filtering your blood. Toxins build up in your brain that’s already not getting enough blood and eventually shuts down and you die.