India’s expanding maritime capabilities are entering a new phase with the induction of a new generation of indigenous naval platforms designed to strengthen combat readiness, hydrographic capability and coastal defence.
The commissioning of INS Dunagiri, INS Sanshodhak, INS Agray and, most recently, INS Mahendragiri reflects the Indian Navy’s growing ability to build a balanced, technologically advanced fleet capable of safeguarding national interests across the Indian Ocean Region.
Designed and built in India with high indigenous content, the Nilgiri-class stealth frigates, Sandhayak-class survey vessels and Arnala-class anti-submarine warfare shallow water crafts represent three distinct yet complementary pillars of India’s maritime security architecture. Together, they reinforce the country’s commitment to Aatmanirbhar Bharat while supporting the Blue Economy and strengthening India’s position as a leading maritime power.
A layered approach to maritime security
India’s maritime responsibilities extend across a coastline of about 11,098 kilometres, an Exclusive Economic Zone of nearly 2.4 million square kilometres and vital sea lanes that carry close to 90 per cent of the country’s trade by volume. Meeting these responsibilities requires a fleet capable of operating across different maritime environments and mission profiles.
The latest indigenous warship classes have been developed to fulfil these diverse operational requirements. While the Nilgiri-class frigates provide frontline combat capability, the Sandhayak-class survey vessels enhance hydrographic operations and the Arnala-class shallow water crafts strengthen coastal anti-submarine warfare. Besides their specialised roles, all three classes are capable of undertaking humanitarian assistance, disaster relief and search-and-rescue missions.
Nilgiri class: The Navy’s next-generation stealth combatants
At the forefront of India’s surface combat capability are the Project 17A Nilgiri-class stealth frigates, designed for multi-mission operations in high-intensity maritime environments. Built with reduced radar, thermal and acoustic signatures, these warships are engineered to remain difficult to detect while delivering powerful offensive and defensive capabilities.
The Nilgiri-class includes INS Nilgiri, INS Himgiri, INS Taragiri, INS Udaygiri, INS Dunagiri, INS Mahendragiri and the under-construction Vindhyagiri. Four ships have been built by Mazagon Dock Shipbuilders Limited in Mumbai, while Garden Reach Shipbuilders and Engineers Limited (GRSE), Kolkata, is constructing the remaining three.
The recent commissioning of INS Dunagiri and INS Mahendragiri further strengthens India’s maritime presence across the Indian Ocean.
Measuring around 149 metres in length and displacing approximately 6,670 tonnes, the frigates are powered by a Combined Diesel or Gas (CODOG) propulsion system, enabling speeds of up to 28 knots. Equipped with BrahMos supersonic missiles, medium-range air defence missiles, advanced radar systems, hull-mounted sonar and helicopter facilities, they are capable of carrying out anti-air, anti-surface and anti-submarine operations.
Project 17A also marks India’s transition from being largely dependent on imported frontline warships to designing and constructing advanced stealth frigates domestically through the Navy’s Warship Design Bureau.
Sandhayak class: Mapping the oceans for security and growth
While combat capability is essential, effective maritime operations also depend on detailed knowledge of the seas. The Sandhayak-class Survey Vessel (Large) strengthens India’s hydrographic capability by mapping the seabed, collecting oceanographic data and producing accurate nautical charts that support both naval operations and commercial navigation.
The class comprises INS Sandhayak, INS Nirdeshak, INS Ikshak and INS Sanshodhak, all built by GRSE in Kolkata. INS Sanshodhak, commissioned recently, is the fourth and final vessel of the class.
Each vessel measures around 110 metres in length, displaces about 3,400 tonnes and has an operational range of approximately 6,500 nautical miles. Equipped with multi-beam echo sounders, side-scan sonar systems and autonomous underwater vehicles, these ships are capable of conducting detailed seabed surveys. They can also operate helicopters and serve as hospital ships during emergencies.
India’s hydrographic efforts have already produced significant results, with Indian hydrographers surveying about 89,000 square kilometres and producing 96 nautical charts between 2019 and 2024, supporting not only India’s maritime interests but also those of friendly countries across the Indian Ocean Region.
Arnala class: Defending the coastline
Closer to shore, the Arnala-class Anti-Submarine Warfare Shallow Water Crafts provide an important layer of coastal defence by detecting and neutralising submarines operating in shallow waters where larger warships have limited manoeuvrability.
The eight-ship Arnala class comprises Arnala, Androth, Anjadip, Amini, Abhay, Agray, Akshay and Ajay. Built jointly by GRSE and L&T Shipbuilding, these vessels are replacing the ageing Abhay-class corvettes. INS Agray was recently commissioned as the fourth vessel in the class, while a parallel Mahe-class is under construction at Cochin Shipyard, increasing the planned fleet strength to 16 shallow water anti-submarine warfare crafts.
Around 77.6 metres long and displacing approximately 900 tonnes, the Arnala-class vessels are powered by waterjet propulsion systems that provide superior agility in shallow waters. They can attain speeds of about 25 knots and are equipped with lightweight torpedoes, anti-submarine rockets, specialised sonar systems and integrated combat management systems.
INS Arnala also holds the distinction of being the largest waterjet-propelled warship inducted into the Indian Navy.
Indigenous shipbuilding driving self-reliance
India is shifting from importer to exporter of naval platforms. GRSE, builder of the survey and ASW classes, is executing overseas orders. National defence exports hit a record Rs 23,622 crore in 2024-25, up about 12 percent over the defence exports figures of FY 2023-24, which were Rs 21,083 crore.
The development of these warship classes reflects the growing maturity of India’s indigenous defence manufacturing ecosystem. The Nilgiri and Sandhayak classes have been designed by the Indian Navy’s Warship Design Bureau, while the Arnala and Mahe classes have been developed by Indian shipyards.
The Project 17A programme incorporates about 75 per cent indigenous content, while the Sandhayak-class survey vessels exceed 80 per cent indigenous content. Across the Navy, 64 of the 66 ships and submarines currently on order are being built within the country.
Building these classes in series sustains shipyards and a wide vendor base. The Project 17A frigate line engaged over 200 MSMEs and about 4,000 direct jobs. It created over 10,000 indirect jobs, and the Arnala-class adds a GRSE and L&T Kattupalli partnership.
Supporting India’s maritime vision
The contribution of these indigenous platforms extends beyond defence preparedness. Survey vessels improve navigational safety and facilitate the Blue Economy by supporting offshore energy, fisheries and maritime trade. Stealth frigates strengthen India’s role as a preferred security partner across the Indian Ocean, while anti-submarine crafts secure coastal waters, allowing larger combat vessels to focus on blue-water operations.
The expanding indigenous fleet also supports India’s maritime initiatives under the SAGAR (Security and Growth for All in the Region) and MAHASAGAR (Mutual and Holistic Advancement for Security and Growth Across Regions) visions by enhancing regional cooperation, maritime security and humanitarian assistance capabilities.
As India continues to strengthen its maritime footprint, the Nilgiri, Sandhayak and Arnala classes stand as symbols of the country’s growing technological capability, indigenous defence manufacturing strength and long-term commitment to safeguarding its maritime interests across the Indian Ocean Region.
