All living species need water for existence and survival.
All the oxygen-dependent species require water, which assists them in the process of respiration.
Water helps in the regulation of temperature, which further assists in the chemical reactions essential for cellular processes like respiration.
In plants, water helps in the process of photosynthesis, that is, the process, which helps to convert sunlight into food.
In animals, water helps in respiration and other basic cell activities.
The body of organisms like humans is made up of 70 percent water, which acts as a most essential medium, via which the biochemical activities of the cell take place.