Good news for Kolkata natives soon metro passengers will able to travel through India's first underwater metro tunnel. The work on India's first metro rail line under the Hooghly river is almost complete and the service is expected to start soon announced Union Railway Minister Piyush Goyal on Thursday. The East-West Metro passageway will pass through under the river and it will become the first such river crossing in the country. Along with the announcement,  Piyush Goyal also gave us a glimpse of India's first underwater metro. On Thursday Piyush Goyal announces that India to get its First Underwater Metro in Kolkata by 2021.

Taking to his Twitter handle, Piyush Goyal wrote in Hindi, "The underwater train is an "example of excellent engineering. This train is a representation of the progress of the Indian railway in the country. With this, Kolkata residents feel comfortable and the country will feel proud".

For the first time in India, a transport tunnel is going to build inside the river. Two tunnels are constructed on the up and down line, which is about 1.4 kilometres long. The width of the Hooghly river is about 520 meters and this tunnel passes through the river bottom.

As per Kolkata metro website, the tunnel will enable the metro to travel more than a 10 storied building below the water surface for almost half a kilometre across the Hooghly river. The reinforced concrete segmental tunnel linings have a thickness of more than a quarter of a metre and are caulked with a gasket of neoprene and hydrophilic rubber to seal the tunnel from ingress of water. This marvel of modern technology is India's first rare venture.   

This project has been in progress since 2009. It is expected that this line will be fully functional in 2021. On this line, Howrah and Sealdah stations of Indian Railways will be present. Railways are expecting about 10 lakh people to use this line of Kolkata Metro by the end of 2035.