Water conducts heat better than water, so you lose body heat to water more easily than to air of the same temperature.
Work Step by Step
Table 14-4 shows that air is a much poorer conductor of heat than water is. Your body will lose heat to the water about 24 times faster than to the equal-temperature air. You feel cold. Also, water has a relatively high heat capacity, so if you are in a pool, as heat leaves your body, the water close to your body stays cold. However, when you are in air, your body heat warms the air close to it. The temperature difference between your body and its surroundings also affects how cold you feel.