Knowing the human body is 60% water, and that some organisms live in water, what is the importance of temperature regulation?

The importance of temperature regulation is to keep the enzyme produced by the body in the optimal range. Enzyme is a protein that can be denaturated in higher temperature but works slowly in lower temperature. That is why the enzyme needs to keep on the optimal temperature. 
The high amount of water in the body will help distribute the heat. Water also need high thermal energy to increase its temperature so it will stabilize the temperature.