Silent sentinels

Mini-submarines are emerging as a critical layer in India's maritime warfare

7 min read

Updated On: Jun 10 2026 | 7:30 AM IST

Mini-submarines, shipping routes, Strait of Hormuz,

Iran’s indigenious Ghadir-class midget submarine, also known as the IS-120, in a shipyard. They were specifically developed for cruising within the shallow waters of the Persian Gulf (Photo: IRNA)

With Iran’s Ghadir-class mini-submarines demonstrating how small underwater platforms can threaten critical shipping routes like in the Strait of Hormuz, similar submarine concepts have drawn attention for their role in maritime operations.

From the shallow waters near coastlines to crowded maritime chokepoints, these smaller and stealthy underwater platforms can perform missions that conventional submarines cannot.

Countries across the world, including the United States (US), Italy, Pakistan and North Korea, operate these vessels. India, too, is exploring such capabilities as the Indian Navy is looking to strengthen underwater operations and special forces deployment.

These so-called midget submarines or special operations vehicles (SOVs) are meant to carry the Indian Navy’s elite Marine Commandos (MARCOS), conduct surveillance and operate in the shallows, where larger submarines struggle to manoeuvre.

Interest in such submarines grew after the 26/11 Mumbai terrorist attack in 2008, exposing gaps in coastal security and the capability to carry out special underwater operations.

AIP gap adds to India's submarine challenge

Private company Larsen & Toubro (L&T) has been developing a midget submarine — the SOV400 — which is powered by a diesel-electric engine.

Arun Ramchandani, senior vice-president and head, precision engineering and systems, L&T, said mini-submarines are becoming popular because naval doctrines are moving beyond large blue-water ships.

“As asymmetric warfare proves to be a game changer in battlefields all over the globe and as maritime competition intensifies across the Indian Ocean Region (IOR), naval doctrines worldwide are increasingly evolving beyond traditional blue-water platforms and moving towards agile, stealth-oriented and distributed undersea capabilities,” said Ramchandani.

“Over the past eight years, L&T has invested in research and development to develop the design of a mini-submarine tailored for Indian Navy requirements,” Ramchandani said.

According to the company, these submarines are fitted with twin torpedo tubes, modern sonar and advanced radio-electronic sensors for detection, surveillance and communication systems. It can provide both credible deterrence and the capability to deploy and recover special forces personnel during covert operations.

The submarine is around 54 metres (m) long with a pressure hull diameter of 4.8m, a maximum operating depth of 150m and a crew capacity of 13 personnel along with 12 MARCOS. In comparison, large conventional submarines are more than 60m long and can operate at depths of around 300-450m, although exact parameters remain classified.

He said that the platform’s functional design has already been completed and cleared by DNV, an international body that certifies maritime and offshore systems for safety and technical standards.

“With functional design completed and approval in place from DNV, L&T SOV is now ready for realisation,” said Ramchandani.

He added that these mini-submarines could act as an intermediate capability between conventional submarines and future unmanned underwater systems.

Designed with low acoustic signatures, they can enhance stealth for covert missions, while also offering manoeuvrability in shallow and congested littoral waters at a low operational cost compared with conventional submarines.

“Mini-submarines offer a practical and combat-ready bridge between conventional submarines and future autonomous systems while also serving as mother platforms for deploying and coordinating unmanned underwater assets as those technologies mature,” said Ramchandani.

He added that L&T has continued developing the submarine despite the absence of firm orders, while also working to increase indigenous content across critical underwater systems with global equipment suppliers to explore localization in these submarines.

However, experts caution that while mini-submarines can strengthen India’s underwater operations, they cannot replace a larger conventional submarine fleet, but complement it.

“There is a tendency to romanticise small submarines because they appear cheap, stealthy and asymmetric. But they remain highly constrained platforms with limited endurance, payload and survivability,” said Vice Admiral Pradeep Chauhan (retired), director-general, National Maritime Foundation, a New Delhi-based defence think-tank.

“A midget submarine is not a replacement for a conventional submarine fleet. It is a specialised supplement for specialised missions.”

Chauhan added that the real strength of mini-submarines lies in access rather than firepower. Unlike large diesel-electric submarines that require large underwater manoeuvring space, mini-submarines can operate in shallow and confined waters.

“A normal diesel-electric submarine requires not just depth beneath the keel but a volume of water to manoeuvre. Once you move into depths below roughly 30–35 m, regular submarines become operationally constrained. That is where midget submarines become useful,” Chauhan explained.

This operational niche becomes relevant for India due to its 11,098.81-kilometres long coastline, islands and busy littoral waters. It can conduct reconnaissance, anti-infiltration patrols, mine-laying and seabed monitoring.

For special forces such as MARCOS, it can be used for covert insertion and extraction, reducing exposure of larger and more expensive ships.

The debate around mini-submarines has intensified after Iran used them as part of swarm tactics in the Strait of Hormuz. However, Chauhan cautioned about comparing India’s maritime geography directly with Iran’s.

“The Strait of Hormuz is adjacent to Iran. The Iranian coast ends and the Strait of Hormuz begins. That proximity fundamentally changes the operational equation,” said Chauhan.

He gave the example of the Strait of Malacca — a possible chokepoint against Chinese shipping often discussed by strategists — as presenting very different operational realities because of heavy traffic, international oversight and distance from Indian shores.

“Can such midget submarines sensibly be deployed in the Strait of Malacca? No. Even if you could insert them there, the real question is — how will they survive, sustain and withdraw?”, Chauhan said, while adding that once a midget submarine attacks a target, its approximate position is compromised and unlike larger submarines, it does not have the speed or endurance to rapidly escape the area.

Even so, Chauhan said mini-submarines could still strengthen India’s maritime posture in the IOR if integrated as part of a layered underwater warfare strategy rather than being taken as standalone deterrent assets.

The mini-submarine programme has now reached an advanced stage of technological maturity as the L&T design has already achieved Technology Readiness Level (TRL) 5-6 — a benchmark to assess the maturity of a technology system, where 5-6 indicates that the platform has moved beyond design and has undergone validation and testing in operational conditions.

“Given the maturity of L&T’s design and that the development has reached TRL 5-6, it is essential that the tender is released under the indigenously designed, developed and manufactured (IDDM) category even at the risk of limited or no competition,” said Ramchandani.

He also indicated that the Indian Navy’s procurement process for mini-submarines is moving forward. “The Indian Navy is at an advanced stage of tender issuance and is expected to obtain the Acceptance of Necessity from the Ministry of Defence within the next six months,” Ramchandani said, while emphasising that these submarines can strengthen India’s deterrence against both Pakistan and China.

The requirement for mini-submarines has existed for years and has moved slowly amid wider acquisition delays for other programmes, with current conventional strength same as in the late 1990s, affecting underwater readiness in the IOR.

The challenge remains between balancing ambition with industrial progress as the L&T project highlights the growing role of private industry. The future of indigenous mini-submarine capability will depend on whether the government converts long-standing interest into actual procurement and sustained production.

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Written By :

Martand Mishra

Martand Mishra has started his reporting career with defence coverage. He is a graduate of the Indian Institute of Mass Communication. He enjoys reading books on defence, history and biographies.