The first of the Indian Navy's six Scorpene-class submarines has successfully floated in water, marking the nearing of its completion at Mumbai's Mazagon Docks (MDL).

The Sunday Guardian quoted an unidentified Indian Navy source as saying: "Both the pressure and the outer hull of the first Scorpene are in place. Much of the internal fit is also progressing well.

"The submarine will now be placed on a pontoon, and tugged out of MDL docks to the nearby Indian Navy Dock. This will free one precious submarine-building dock at MDL, and thus help in meeting deadlines for subsequent Scorpenes. The remaining work on the first submarine, in particular the fitment of batteries, will be done in the naval dock."

Following its fit out, the submarine will undergo harbour and sea trials to validate its weapons firing capability before commissioning it into official service with the Indian Navy.

"Both the pressure and the outer hull of the first Scorpene are in place. Much of the internal fit is also progressing well."

Delivery of the first submarine is expected in September 2016, with the remaining vessels scheduled to be handed over every nine months, according to the news agency.

The first Scorpene-class vessel was originally scheduled for delivery in December 2012.

In October 2005, a contract was awarded to DCNS to build six Scorpene-class submarines, as part of the Rs187.98bn ($4.16b) Project 75.

The 1,750t Scorpene-class vessels will feature a sonar suite that consists of a long-range, passive cylindrical array, intercept and active sonar, distributed and flank array, as well as a high-resolution sonar for mine and obstacle avoidance, and a towed array.

Powered by two diesel generation sets and armed with SM-39 Exocet anti-ship missiles, the 67m-long submarines can dive up to a depth of 300m, require minimum manning and help reduce lifecycle costs.