Water serves as a rinsing medium which prevents the stone‘s pores from clogging with abrasion debris and preserves its abrasion qualities. If the stone is not enough rinsed with water, the abrasion debris makes a paste that decreases the stone‘s abrasion qualities. Professional sharpeners make use of this principle to achieve a finer abrasion in order to compensate greater steps in grit.
The stones must be soaked in water for 10-15 minutes before use. Ceramic stones like Shapton stones hardly absorb water. With them, 1 minute of soaking is enough.
Waterstones differ with regard to their bond as well as to their abrasive.