It is not related to common rice.
Wild rice is a summer annual that is commercially grown in shallow lakes or man-made paddies.
Wild rice seed germinates in the spring and is harvested by boat or combine in late summer. After harvest, the large wild rice seeds are steamed, dried, dehulled, and cleaned to produce the dark brown grain that is marketed around the world. Although wild rice has been hand-harvested in lakes for thousands of years, paddy production and combine harvesting is a recent development. Wild rice was introduced into California in the 1970's. The first commercial harvest in Oregon was in 1991, and the first processing plant in the state was built in 1994.