Long Island Sound is an estuary, a place where salt water from the ocean mixes with fresh water from rivers draining from the land. Like other estuaries, Long Island Sound abounds in fish, shellfish, and waterfowl. It provides feeding, breeding, nesting, and nursery areas for diverse animal and plant life. Long Island Sound also supports many recreational and commercial uses. More than 8 million people live in the Long Island Sound watershed and more than 20 million live within an hour's drive from the shore. This report, Sound Health 2003, an update to a similar report to the public published two years ago, provides a sample of the more than 40 specific environmental indicators used to assess the ecological condition of the Long Island Sound.