Final answer:
When immersed in cold water, it is best to stay still and conserve energy to maintain body heat rather than swim vigorously or drink cold water. The body naturally tries to conserve heat in cold situations by reducing blood flow to the extremities and becoming lethargic.
Step-by-step explanation:
If you are immersed in cold water and can't get out, the best action to take is to stay still and conserve energy. When your body reacts to cold, it begins behaviours like shivering to return to a stable temperature, otherwise known as homeostasis. Vigorous movement, such as swimming or performing jumping jacks, can increase heat loss from your body and may lead to faster hypothermia. Drinking cold water is also not advisable as it can lower your core temperature. Instead, it's crucial to conserve as much body heat as possible by keeping movement to a minimum and staying as calm as you can.
For C.J. stuck in her car during a blizzard, her body would conserve heat by becoming lethargic, not by increasing the blood flow to the hands and feet. In fact, the body would likely reduce blood flow to extremities to keep the vital organs warm.
When in the water, the body's instinctive reaction might not be helpful for calling for help as the muscular spasm that seals the airway prevents shouting. The primary focus should be self-preservation through energy conservation and body heat retention until rescue is possible. This is similar to how an endothermic animal would react to sudden drops in environmental temperature by increasing muscle activity to generate heat, though in the case of cold water immersion, minimizing muscle activity is key.