Step 1: Understand the significance of the project.
An underwater metro is a major engineering feat where metro tunnels are bored under a riverbed. This was a first for India.
Step 2: Identify the city and the river.
The first underwater metro service in India was launched in Kolkata. The metro line runs under the Hooghly River, connecting the cities of Kolkata and Howrah.
Step 3: Know the details of the launch.
This specific section is part of the Kolkata Metro's East-West corridor (or Green Line). It was officially inaugurated in March 2024, marking a historic moment for India's infrastructure development. Kolkata also has the distinction of being the first city in India to have a metro rail system, which started in 1984.