Severe hypothermia causes loss of consciousness and may result in death. Cold water is especially dangerous because loss of body heat occurs 25 times faster in cold water than in cold air. How quickly you become hypothermic depends on many factors, including your personality and behavior, environmental factors, how you are dressed, and your physical condition. Everyone reacts differently to the cold, even under the same conditions. Generally, children lose body heat more quickly than adults.
Thin people lose body heat faster than overweight people.
The expected survival times in Table 1 are guidelines for the average adult, showing the rapid onset of hypothermia as water temperatures drop. Water this cold always presents the danger of hypothermia. Some northern Minnesota lakes are cold year-round. When you first fall into cold water you gasp, your skin begins to cool, and your body constricts surface blood vessels to conserve heat for your vital organs. Blood pressure and heart rate increase.