Indian Island County Park Cross River Drive, Riverhead, NY11901 Indian Island County Park is known as The Mouth of the Peconic. It is the spot where the North Fork and South Fork…More of Long Island meet. It is also where the freshwater of the Peconic River and saltwater of Flanders Bay meet. The site of a number of outdoor activities and facilities, there are 137 campsites that accommodate tents, trailers and recreational vehicles. There are warm-water showers, RV hookups and a dump station that is available in the summer. It also offers picnicking, boating, fishing, hiking and more. Indian Island Golf Course, open to the public, is adjacent to the park.