Not very deep.
Lake Pontchartrain
lake, southeastern Louisiana, U.S. The lake is 40 miles (64 km) long and 25 miles (40 km) wide at its widest point, with an area of 630 square miles (1,631 square km) and a mean depth of 10 to 16 feet (3 to 5 metres). It is more a tidal lagoon than a lake, since it connects eastward through Lake Borgne with the Gulf of Mexico by a narrow passage called The Rigolets.
Thanks, I didn't think it was very deep. Looking at the slabs of cement sitting sideways on the causeway it looked very shallow. Isn't a lot of this because of the silt that washes in when they dump Mississippi water into her during flood events?