It is the biggest underwater river tunnel of India, which is made for metro rail service.

Even on the new alignment a station planned at Wellington had to be dropped as Government of West Bengal was unable to provide the required land on the surface.

The Howrah metro station on the west side of the river will be at a depth of 30 metres (98 ft 5 in).

[7] As the work began, the national & regional media claimed this project as a big milestone terming India's first under water and “underwater river” metro tunnel, but it's not true.

The Metro authorities deemed the Esplanade-Sealdah section (particularly the incomplete, caved-in west-bound tunnel), to be challenging and impossible to finish by 2023.

For this, the authorities brought two racks from Central Park depot to Esplanade metro station on 9 April 2023.

From there, the wheels of railways rolled for the first time below the Hoogly river when, both trains arrived at Howrah Maidan station on 13 April 2023.

[10] Later, Kolkata Metro added blue light in the underwater tunnel section to give passengers a sense of feeling under Hooghly River.

[13][14][15] Just before the tunnel enters the underwater segment, lies a ventilation shaft on the Kolkata bank of Hooghly River, which is the deepest of its kind in India, at 44 metres (144 ft) below ground level.