The Best Beaches that i know in Kerala, Kovalam beach, Trivandum.
Varkala Beach, Trivandrum.
Cherai Beach, Ernakulam.
Marari Beach, Alappuzha.
Kannur Beach.
Recently heard about Revdanda beach near Chaul in Maharashtra to be a really good beach to visit especially when you are expecting peace and serenity :)
The second-longest beach in the world and India's longest beach are both located in Chennai along the Gulf of Bengal. From Beasant Nagar in the south to Fort St. George in the north, this mostly sandy 12-kilometer stretch.