The Periyar Lake is not a lagoon.
Ashtamudi Lake, Chilika Lake, and Pulicat Lake are all examples of lagoons. A lagoon is a shallow body of water separated from the open sea or ocean by a barrier, such as a sandbar, barrier island, or coral reef. Lagoons are typically characterized by brackish or saline water and are found along coastal areas.
Periyar Lake, on the other hand, is a reservoir formed by the construction of the Mullaperiyar Dam on the Periyar River in Kerala, India. It is not a lagoon but an artificial lake created for water storage and hydroelectric power generation purposes.