Another large highway project is scheduled to be inaugurated in Mumbai. A 9 kilometer section of the 'Coastal Road' (also known as the Western Freeway) will be inaugurated on February 19, from the Bandra-Worli Sea Link in the north to Marine Drive in the south.
Most of the project is a structure along the coast, but it also includes a tunnel under a hill and under a beach, making it a de-facto undersea tunnel (though only marginally offshore).
The only decent size photos I could find seem to be from a while ago.
(https://i.imgur.com/ADK5O0p.jpeg)
(https://i.imgur.com/hw5gqbP.jpeg)
(https://i.imgur.com/hlV1zis.jpeg)
First section of this should open in May. It will be an incredibly impressive road. It will surely have traffic jams but will be worth it to increase mobility.
https://www.worldhighways.com/wh8/news/indias-us17-billion-mumbai-coastal-highway