The water chestnut, also called the Chinese water chestnut or the water caltrop, is a tuber vegetable that resembles a chestnut in color and shape. Although it is most commonly associated with Chinese cooking, it is now gaining in popularity as a cooking ingredient in many different ethnic meals. Originating in Southeast Asia, water chestnuts are the roots of an aquatic plant that grows in freshwater ponds, marshes and lakes, and in slow-moving rivers and streams. Currently, water chestnuts are grown in Japan, Taiwan, China and Thailand as well as in Australia. When harvesting water chestnuts, much labor is involved. Because of this, water chestnuts are fairly expensive to purchase, especially in a processed or canned form. However, processed and canned water chestnuts are the most common form used for producing and mass-marketing water chestnuts to consumers. You can easily purchase these products in most supermarkets and grocery stores. You can also purchase fresh water chestnuts, which are more difficult to find, at some specialty vegetable stores and ethnic markets. When purchasing fresh water chestnuts, however, know who your supplier is first to ensure that the tubers, which you are buying, are fresh. Once you have purchased your water chestnuts, if canned, you can store them unopened in your home pantry. If a can has been opened or if you have purchased fresh water chestnuts, you can store them for up to one week in your refrigerator. However, you must keep the water chestnuts in a bowl of water. The water must also be changed every day in order for them to remain fresh while they are being stored.