Water chestnuts are the edible fruit of an aquatic plant native to Southeast Asia. They are encased in a black skin that must be peeled away. The flesh is crisp, white and slightly sweet. Since they are quite starchy, water chestnuts are used as a vegetable in Asian cooking and also ground to make water chestnut powder (or flour), which is a thickener similar to cornstarch. Fresh water chestnuts can usually be found in Asian markets, but the bulk of the American supply comes canned either whole or sliced. Typically used as an ingredient in stir-fries, water chestnuts are also added to salads, pilafs and entrées for their crunchiness.