Kolkata in India is set to test the country's first underwater Metro on the Hooghly River with two six-coach trains undergoing a trial run on the 4.8 km stretch between Esplanade and Howrah Maidan. The trains for the test will run from the Salt Lake depot to Howrah Maidan through the east-bound tunnel between Sealdah and Esplanade, using a battery-powered loco since the incomplete tunnel doesn't have electrified third rails. This milestone will be keenly followed by KMRC officials and railway enthusiasts across the country.