Answer:
The human body has an internal temperature of 98.6°F or 37°C. When a person is submerged in water thats much cooler than their own body temperature, it makes it difficult to maintain the bodys heat. As we know, our body shivers when we get cold; but the shivering alone wouldn't be enough to keep your body warm in the cold water. Since this is so, you wouldn't last long without going into hypothermia.
