No matter how I do the math I am coming up with number around 5% of population

City/Town State Coast Approximate Population
Mumbai Maharashtra West Coast 20+ million
Chennai Tamil Nadu East Coast 8 million
Kochi Kerala Southwest 2.1 million
Vishakhapatnam Andhra Pradesh East Coast 2+ million
Goa (Panaji, Vasco da Gama, Margao, etc.) Goa West Coast Around 1 million
Mangalore Karnataka West Coast Around 600,000
Kanyakumari Tamil Nadu Southern tip Around 22,000
Puducherry (Pondicherry) Puducherry East Coast Around 950,000
Kollam Kerala West Coast Around 360,000
Thiruvananthapuram Kerala West Coast Around 950,000
Vizianagaram Andhra Pradesh East Coast Around 300,000
Daman and Diu Union Territory West Coast Around 220,000
Alibag Maharashtra West Coast Around 20,000
Paradeep Odisha East Coast Around 130,000
Ratnagiri Maharashtra West Coast Around 76,000
Karaikal Puducherry East Coast Around 70,000
Rameswaram Tamil Nadu East Coast Around 40,000
Surat Gujarat West Coast Around 6 million
Veraval Gujarat West Coast Around 46,000
Vengurla Maharashtra West Coast Around 12,000
Mahabalipuram Tamil Nadu East Coast Around 12,000
Karwar Karnataka West Coast Around 30,000
Ganpatipule Maharashtra West Coast Around 2,000
Total Population     Approximately 42.5 million