To be christened as Vagir, it is the fifth of six French-designed Scorpene-class submarines.
As part of the trials, the vessel’s systems, such as propulsion systems, weapons and sensors will be put through ‘intense’ testing at sea.
It is set to be handed over to the Indian Navy later this year.
In November 2020, the submarine was launched from Mazagon Dock Shipbuilders Limited’s (MDL) Kanhoji Angre Wet Basin.
In a statement, Indian Navy said: “Despite the Covid pandemic, MDL has ‘delivered’ two submarines of the Project – 75 in the year 2021 and the commencement of sea trials of the fifth submarine is a significant milestone.”
MDL is constructing the six submarines via technology transfer from France-based Naval Group.
Two submarines, INS Kalvari and INS Khanderi, have already been commissioned into the Indian Navy.
INS Karanj, the third submarine, was commissioned at the Naval Dockyard Mumbai in July 2021.
In November last year, the Indian Navy received the fourth submarine INS Vela and was commissioned into service the same month.
The sixth submarine, Vagsheer, is currently under construction.
In July last year, the Indian government issued a request of proposal for Project 75 (I) involving the construction of six air-independent propulsion (AIP) fitted conventional submarines.