Or actually having better, purer water.

If, for example, your area is known for its "safe but smelly water" and you have a natural artesian well that pours out laborartory tested, scientifically proven "pure" water, free of all the contaminants found in the typical domestic water supply, AND you could set up a bottling and distribution operation ...

My point is, with the right opportunity, the right product, at the right time, marketing often takes care of itself after only an initial launch.

OTOH, if you're filling bottles with filtered or "purified" tap water and selling it as something special, your in for the long haul.