Generally speaking, water starch is dry starch. Adding water is called water starch. You don't need to buy it, you can do it at home.

Fried things are usually dry starch, or dry starch with egg liquid. Starch used for thickening, also known as dough powder, is a polysaccharide polymer concentrated by multiple glucose molecules. Starch used for cooking mainly includes mung bean starch, potato starch, wheat starch, water chestnut starch and lotus root starch. Starch is insoluble in water. When it is heated to 60℃ with water, it will be gelatinized into a colloidal solution. Thickening is the use of this property of starch.