Coconut water is composed of many nutrients such as sugars,vitamins,minerals,electrolytes,enzymes, amino acids, cytokine, and phyto-hormones.
It is a very good source of B-complex vitamins such as riboflavin, niacin, thiamin, pyridoxine, and folates. These vitamins are essential in the sense that the human body requires them from external sources to replenish.
In case of diarrhea: Coconut water carries a very good amount of electrolyte potassium and replenish electrolyte deficiency in the body due to diarrhea.
Coconut water is sterile - that is, free of bacteria and the like. In an absolute emergency, coconut water can be used as an alternative to blood plasma, but you're much better off just drinking it.