Thermal Properties
The range of temperature variatidn in the aquatic environment is smaller in comparison to air. This means the rate of change of temperature is slower in the aquatic environment than in air. This is because of unique thermal properties that minimise temperature changes. The temperature of liquid water rises and falls relatively slowly as compared to most other liquids. One calorie of heat energy is required to raise the temperature of one gram of water by one degree Celsius. This is about twice the amount of energy required by other covalently bonded liquids to bring about a similar temperature change. The many hydrogen bonds that link water molecules together absorb heat to a considerable extent without any corresponding change in temperature. Temperature of water drops slowly on losing heat.
Specific Heat
The heating and cooling of the water is relatively slow as compared to most of the other known liquids. This is mainly because the water molecules are linked with each other by hydrogen bonds. If the water is to evaporate, the hydrogen bonds will have to be broken and this requires energy. The specific heat of water is 4.18 joule (1 calorie per gram per degree centigrade). This means that it takes 4.18 joule of energy to heat one gram of water from 4oC to 5oC.