India’s first underwater train in Kolkata is all set to be fully completed by 2023. The Kolkata Metro Rail Corporation (KMRC) has made a way to pass under the Hooghly River. The train will be 13 metres below the Hooghly River. The train will be running at a depth equal to a 10-story structure while underwater. The tunnel is will be built with 1.4 m-wide concrete rings, which will be part of the metro station. The cost of this project is Rs 8,600 crore, roughly.