Explanation:

The Kerala backwaters (locally known as kayals) are a chain of brackish lagoons and lakes lying parallel to the Arabian Sea coast.
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.
What is the difference between backwater lake and lagoon?
Backwater is water turned back in its course by an obstruction on opposing current or the flow of tide as in a sewer or river channel or across the river bar. A lagoon is the area of relatively shallow, quiet water with access to the sea but separated from it by sandbars, barrier island or coral reefs.