This tidal lagoon is the second largest in South America, lying 174 miles long and 44miles wide. It is separated from the Atlantic by a sandbar 5 miles wide, and has 5 rivers that feed into it. The lagoon of ducks gets its name from original settlers who wanted to set up a duck breeding colony.
There are several islands, the largest of which has a human population.
There is a second lagoon to the south called Mirim. These two lagoons together create a large ecosystem which includes reed-bank, and grasses, numerous fish, bird species and even sea turtles which can be found here in spring and summer.