The Kerala backwaters are a network of brackish lagoons and canals lying parallel to the Arabian Sea of the Malabar coast of Kerala state in south-western India. It also includes interconnected lakes, rivers, and inlets, a labyrinthine system formed by more than of waterways, and sometimes compared to bayous. The network includes five large lakes linked by canals, both man made and natural, fed by 38 rivers, and extending virtually half the length of Kerala state. The backwaters were formed by the action of waves and shore currents creating low barrier islands across the mouths of the many rivers flowing down from the Western Ghats range. In the midst of this landscape there are a number of towns and cities, which serve as the starting and end points of backwater cruises. There are 34 backwaters in Kerala. Out of it, 27 are located either closer to Arabian Sea or parallel to the sea. The remaining 7 are inland navigation routes. The backwaters have a unique ecosystem: freshwater from the rivers meets the seawater from the Arabian Sea. A barrage has been built near Thanneermukkom, so salt water from the sea is prevented from entering the deep inside, keeping the fresh water intact. Such fresh water is extensively used for irrigation purposes. Many unique species of aquatic life including crabs, frogs and mudskippers, water birds such as terns, kingfishers, darters and cormorants, and animals such as otters and turtles live in and alongside the backwaters. Palm trees, pandanus shrubs, various leafy plants, and bushes grow alongside the backwaters, providing a green hue to the surrounding landscape. Hydrography National Waterway 3 from Kollam to Kottappuram, covers a distance of and runs almost parallel to the coastline of southern Kerala facilitating both cargo movement and backwater tourism. Vembanad is the largest of the lakes, covering an area of . The lake has a large network of canals that meander through the region of Kuttanad. The important rivers from north to south are the Valapattanam , Chaliyar , Kadalundipuzha , Bharathappuzha , Chalakudy , Periyar , Pamba , Achankovil , Meenachil , and Kalladayar . Other than these, there are 35 more small rivers and rivulets flowing down from the Ghats. Most of these rivers are navigable up to the midland region, in country crafts. Vembanad Lake is the longest backwater in Kerala, as well as the longest lake in India. The Kochi city,