FDN-2 is India's first indigenously-built floating dock.
L&T had won the contract in May, 2015 to design and build the FDN-2 at a cost of Rs 468 crore.
"The floating dock will be delivered at Port Blair well within the contracted schedule," the L&T said in a statement.
On completion of its launch at Kattupalli, FDN-2 would be put through a series of harbour trials before delivery to the Navy.
The floating dock was lowered into the waters of the Bay of Bengal by Anjali Deshpande, wife of Vice Admiral D M Deshpande, Controller, Warship Production and Acquisition, the Indian Navy.
FDN-2 which is the first naval shipbuilding project for L&T, is 185 metres long and 40 metres wide, and is designed for docking Indian Navy ships and submarines of up to 8,000 tonnes of displacement.
"While winning our first mandate from the Indian Navy was satisfying, I am particularly delighted that we have also been able to execute and deliver the FDN-2 well within schedule," said S N Subrahmanyan, Managing Director (Designate) and President, Larsen and Toubro.
L&T's Senior Executive Vice President and Whole-time Director (Designate) of Defence J D Patil said, "It is an affirmation of the in-house capabilities and track record of L&T that we are launching the FDN-2 for the Indian Navy ahead of schedule today".
L&T has also been mandated by the Coast Guard to design and build seven Offshore Patrol Vessels (OPVs). Two of these OPVs are to be launched in the second half of this financial year, on schedule.
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