They may be right, as water is necessary for almost every function of our body. Therefore, we should drink enough.  However, recent reports suggest that our tap water is contaminated by multiple toxins. So it looks like in order to get enough of the essential nutrient, we have to consume more toxins.
The solution to the problem in my opinion is to drink water free of contamination for sure: distilled water. Because it is made by condensing steam, unless it is contaminated after production, it is virtually free of solid toxins.Only few things are proven to prolong life. Among them drinking . Remember that!