Rio de la Plata - Silver River in Spanish - is neither a river nor silver in color. This semi-enclosed body of water nearly 290 km (180 miles) in length doesn't flow anywhere. It has tides and waves and is a silty brown. What's more, the water of the River Plate, as it is referred to in English, isn't fresh it's brackish. Can you guess what Rio de la Plata might be? It is the place where the freshwater of the Uruguay and Paraná, two of South America's largest rivers, meet the saltwater of the Atlantic Ocean making it an estuary. Like all estuaries, Rio de la Plata is a unique habitat. It is home to plants and animals that require mixed water - part salt, part fresh - to survive. The La Plata Dolphin is one example. And it plays an important role in the environment. The plants and soil of the River Plate filter dirt and pollution just like a sieve.