The Altamaha River /ˈɑːltəməhɑː/ is a major river in the U.S. state of Georgia. It flows generally eastward for 137 miles (220 km) from its origin at the confluence of the Oconee River and Ocmulgee River towards the Atlantic Ocean, where it empties into the ocean near Brunswick, Georgia.There are no dams directly on the Altamaha, though there are some on the Oconee and the Ocmulgee.he Altamaha River flows through a flood plain up to five miles (8 km) wide, consisting of some of the last remaining hardwood bottomlands and cypress swamps in the American South. As the river approaches the Atlantic Ocean, it becomes a broad estuary.