The Laguna Madre is a shallow lagoon extending about 285 miles (456 km) along the coast of the Gulf of Mexico. Its northern part, in Texas, is separated from the Gulf by a long, thin barrier island, Padre Island. The southern part, in Mexico, is similarly cut off by a string of barrier islands. The entire lagoon connects with the Gulf only via a few narrow channels, and it is less than 3 ft (1 m) deep in most parts. It is saltier than seawater because it receives no input of river water and lies in a hot, dry region, leading to high rates of evaporation. Seagrass meadows and several species of crustaceans and fish thrive in the lagoon, which also supports many wintering shorebirds and waterfowl. Threats to its health include coastal development, dredging, overfishing, agricultural pesticides, and algal blooms.