Water is actually an incredible molecule for its small size. It is the basis for all life on earth. Lets look at each of the chemical properties that you listed above. Cohesion is also known as surface tension. Water has a very high surface tension. It's what causes water to bead up on a surface as opposed to spread out into a thin layer. This is due to the extensive hydrogen bonding that occurs in water between the oxygen and hydrogen atoms of neighboring molecules. This cohesion allows water to be more easily contained inside compartments (such as within cellular membranes) without trying to escape (seep out). Specific heat is the energy required to raise the temperature of a chemical. Water has a high specific heat and as a result a high boiling point for such a small molecule. This allows water to maintain its temperature more readily. This helps the body to maintain a steadier temperature constantly without large shifts in either direction. Solubility is the ability for different chemicals to dissolve in a particular medium (solvent). Water is a very polar compound and as such will readily solubilize polar compounds such as inorganic salts and ions. This also means that very hydrophobic biochemicals such as fatty acids will not dissolve at all in water and thus their function will not be impaired. Density is the measure of mass per unit volume. Water actually has a fairly average density of 1gram per milliliter.