Survival skills
A human being can survive an average of three to five days without the intake of water. The issues presented by the need for water dictate that unnecessary water loss by perspiration be avoided in survival situations. The need for water increases with exercise.
Drink
When the human body becomes dehydrated, it experiences thirst. This craving of fluids results in an instinctive need to drink. Thirst is regulated by the hypothalamus in response to subtle changes in the body's electrolyte levels, and also as a result of changes in the volume of blood circulating. The complete elimination of drinks, that is, water, from the body will result in death faster than the removal of any other substance. Water and milk have been basic drinks throughout history. As water is essential for life, it has also been the carrier of many diseases.