Water doesn't actually conduct electricity!
This might sound counterintuitive given everything that you probably know about electricity and water. In fact, however, it is not water that conducts electricity, but rather the impurities in the water.
An electric current is passed when electrons are passed from one atom to the other. However, a basic requirement is that the molecules have to have a charge already for electricity to be conducted.
Distilled water; that is, water that is completely pure and devoid of any other elements, does not have charged molecules, therefore these molecules do not swap electrons. Water in it's purest form cannot conduct electricity, but stuff like salt, calcium and magnesium in sea or fresh water do.