INS Nipun Explained: How India Is Building Deep-Sea Diving and Submarine Rescue Power

• Specialised support vessel: INS Nipun is not primarily a missile-armed destroyer, frigate or conventional combat ship. It is a purpose-built Diving Support Vessel (DSV) designed to support people, equipment and specialised systems working below the sea surface.

• Nistar class: It is the second vessel of India's indigenous Nistar class. INS Nistar is the first vessel of the class and serves on the eastern seaboard, while INS Nipun strengthens the western seaboard.

• Builder: Both ships were designed and built by Hindustan Shipyard Limited at Visakhapatnam. When the two vessels were launched, the Ministry of Defence described them as India's first-of-their-kind indigenously designed and constructed Diving Support Vessels.

• Meaning of the name: “Nipun” comes from Sanskrit and signifies someone who is adept, capable or skilled in a particular discipline—appropriate for a highly specialised vessel.

• Humans cannot simply dive indefinitely: Water pressure rises rapidly with depth. Deep-water work therefore requires specialised breathing systems, decompression procedures, pressure chambers, medical support and mechanisms for safely launching and recovering divers.

• Floating underwater base: A DSV essentially acts as a self-contained offshore base for divers and underwater equipment.

• It can support: underwater inspection of ships and submarines;

underwater maintenance and repair; salvage of damaged or sunken equipment; recovery of objects from the seabed; intervention around underwater structures; search and rescue; submarine emergencies; and operation of ROVs and rescue submersibles.

• Operational advantage: Without a DSV, many complicated missions would depend heavily on shore-based diving facilities or improvised arrangements aboard other ships. A dedicated vessel allows the Navy to remain at the scene for prolonged periods and respond more quickly.

• Growing underwater domain: Modern naval competition increasingly extends below the surface. Submarines, seabed sensors, underwater vehicles and underwater communication infrastructure are becoming more significant.

• Submarine operations: India operates conventional and nuclear-powered submarines. As submarine operations expand, the supporting ecosystem—maintenance, rescue, diving, training and emergency response—must expand with it.

• Indian Ocean geography: India has a long coastline and maritime interests extending deep into the Indian Ocean Region. An underwater emergency may occur hundreds or thousands of kilometres from a major naval base.

• Race against time: A disabled submarine may have limited oxygen, battery power and life-support capacity. Therefore, the ability to locate it, provide emergency assistance and initiate rescue quickly can determine whether the crew survives.

• The value of a DSV is consequently not measured mainly in firepower. It lies in operational endurance and rescue readiness.

• Pressure problem: As a diver goes deeper, surrounding pressure increases. Under higher pressure, gases from the breathing mixture dissolve into the body's tissues.

• When the diver returns towards the surface, pressure must be reduced gradually so these gases can leave the tissues safely.

• Ascending too rapidly can cause bubbles to form inside the body, producing decompression sickness—popularly called “the bends”.

• Saturation principle: During saturation diving, divers remain in a pressurised environment for extended periods. Eventually their tissues become saturated with dissolved inert gas, meaning additional time at the same pressure no longer substantially increases the decompression requirement.

• The divers therefore: live inside a pressurised chamber aboard the vessel;

travel to the underwater worksite in a pressurised diving bell; work at depth; return to the chamber without returning to normal atmospheric pressure after every dive; and undergo one carefully controlled decompression sequence at the end of the mission.

• Operational benefit: Instead of spending hours repeatedly decompressing after every deep dive, the crew can conduct productive underwater work for many days.

• The Nistar-class ships were designed to support saturation diving at depths of around 300 metres.

• Heliox: Heliox is a breathing mixture primarily consisting of helium and oxygen.

• Ordinary air contains a large amount of nitrogen. At high pressure, nitrogen can cause nitrogen narcosis, which impairs judgement, coordination and mental performance.

• Why helium helps: Helium produces much less narcotic effect than nitrogen and is therefore used in deep-diving breathing mixtures.

• Not risk-free: Deep diving still requires careful management of oxygen toxicity, temperature loss, pressure effects and decompression.

• INS Nipun has been designed to support saturation, air and heliox diving, allowing the ship to undertake different categories of underwater operations.

• Controlled pressure environment: A diving compression chamber is a sealed compartment in which atmospheric pressure can be increased or reduced in a controlled manner.

• It can be used to: prepare saturation divers for working depth;

maintain divers under pressure between dives; safely decompress them; treat decompression sickness; and provide emergency hyperbaric medical care.

• Medical significance: Deep-sea diving is therefore inseparable from diving medicine. INS Nipun's dedicated life-support and medical infrastructure is as important as its cranes, ROVs or propulsion systems.

• Emergency evacuation: A conventional lifeboat cannot safely evacuate saturation divers who are living under high pressure because suddenly bringing them to atmospheric pressure could cause serious decompression injuries.

• A hyperbaric lifeboat maintains the required internal pressure while taking saturation divers away from a damaged or endangered ship.

• The Indian Express reported that INS Nipun carries a self-propelled hyperbaric lifeboat, adding an important layer of safety for saturation-diving personnel.

• ROVs: A Remotely Operated Vehicle (ROV) is an unmanned underwater machine connected to a surface vessel through control and communication systems.

• ROVs can carry: cameras;

sonar; lights; robotic manipulators; cutting or recovery equipment; and inspection sensors.

• Human-safety advantage: ROVs can enter depths or environments that are too hazardous or impractical for divers.

• DSV role: They can inspect underwater objects before divers enter the water, observe divers while they work, inspect damaged submarines and assist in salvage operations.

• The Nistar-class platform incorporates ROV systems for underwater monitoring and intervention. For INS Nistar, the Ministry of Defence stated that associated ROVs can undertake monitoring and salvage work to depths of around 1,000 metres.

• Imagine divers working hundreds of metres below a ship while connected through diving bells, cables, hoses and communication systems.

• If the ship drifts significantly because of wind, current or waves, those connections could be damaged or place divers in danger.

• Dynamic positioning: Dynamic Positioning uses navigation sensors, computers, propellers and thrusters to automatically maintain a vessel at a precise location and heading without relying only on an anchor.

• The Ministry of Defence specifically highlights INS Nipun's precise station-keeping capability, while naval reporting identifies dynamic positioning as one of its enabling systems.

• This is especially important during: saturation diving;

ROV deployment; submarine rescue; seabed inspection; and salvage operations.

• A submarine can become disabled because of: collision;

flooding; fire; equipment failure; propulsion problems; explosion; or another underwater accident.

• If it settles on the seabed but its pressure hull remains intact, the crew may still be alive.

• Such a submarine is commonly referred to in rescue terminology as a DISSUB — Disabled Submarine.

• The rescue problem: Rescue forces must first locate the submarine precisely. They must then determine its orientation and structural condition, clear debris if necessary and establish whether a rescue vehicle can safely mate with its escape hatch.

• All this can occur hundreds of metres below the surface in darkness and strong currents.

• A Deep Submergence Rescue Vehicle (DSRV) is a small specialised manned submersible designed to descend from a surface support system, locate a distressed submarine and mate with its rescue hatch.

• India's system can perform rescue operations against a distressed submarine at depths of up to 650 metres. The DSRV has a crew of three and can evacuate up to 14 submariners during an individual rescue cycle.

• A full rescue may therefore require repeated trips between the disabled submarine and the surface support system.

• A rescue can broadly involve several stages.

• Stage 1 — Locate the disabled submarine: Search systems and sonar identify the submarine's position on the seabed.

• Stage 2 — Assess the site: An ROV can inspect the submarine, check the rescue hatch, observe damage and identify debris or obstructions.

• Stage 3 — Emergency assistance: If immediate rescue is not yet possible, an ROV may help deliver emergency life-support equipment.

• India's submarine-rescue system includes Side Scan Sonar and ROV-supported emergency life-support capability.

• Stage 4 — Deploy DSRV: The DSRV descends from the rescue system towards the submarine.

• Stage 5 — Mate with the submarine: The DSRV positions itself over a designated submarine rescue hatch and establishes a watertight connection.

• Stage 6 — Transfer survivors: The hatch is opened and submariners move into the rescue vehicle.

• Stage 7 — Return and medical treatment: Rescued personnel return to the mothership and are assessed for pressure-related and other medical complications.

• This illustrates why rescue capability is a system, rather than merely a submersible.

• Surface command base: A DSRV cannot perform the entire rescue operation independently. It needs a surface vessel that carries the rescue system, crew, support equipment and command facilities.

• The mothership provides: launch and recovery;

positioning over the rescue area; power and maintenance; diving and ROV support; communications; medical facilities; decompression facilities; accommodation and logistics; and command and control.

• INS Nipun and INS Nistar therefore multiply the effectiveness of India's DSRVs by providing purpose-built platforms for operating them.

• This is why commissioning the mothership is almost as significant as possessing the rescue vehicle itself.

• Earlier arrangements: The Navy historically operated Russian-origin submarine rescue vessels and also relied on diving units, shore establishments and other appropriately equipped ships. However, these arrangements lacked the integrated multi-domain capability and long deployment endurance of a modern purpose-built DSV.

• DSRV breakthrough: India acquired an advanced non-tethered DSRV system for the western seaboard in 2018. Its trials demonstrated underwater mating with a submarine and dives beyond 600 metres.

• Second seaboard: A second DSRV subsequently joined the eastern seaboard, giving India one submarine-rescue system for each coast. The Ministry of Defence states that the two systems were inducted during 2018-19.

• Next step: The Nistar-class DSV programme gives these rescue systems purpose-built motherships rather than relying entirely on vessels of opportunity.

• India's DSRV system was designed so that major components can be moved rapidly by air, land or sea to a suitable port near the distressed submarine.

• This is known as a flyaway configuration.

• Why important: A submarine emergency may occur far from the DSRV's home base. Transporting the rescue system by heavy-lift aircraft to the nearest suitable mobilisation port can save crucial time.

• The system can then embark on an appropriate vessel and proceed to the accident location.

• Thus India's rescue concept combines: mobile DSRV + mothership/ship of opportunity + ROVs + sonar + medical support + trained submarine-rescue unit.

• Eastern seaboard: INS Nistar operates under the Eastern Naval Command, headquartered at Visakhapatnam.

• Western seaboard: INS Nipun is intended to strengthen the Western Naval Command's specialised underwater capability from Mumbai.

• Operational logic: India faces the:

• Arabian Sea and western Indian Ocean on one side;

Bay of Bengal and eastern Indian Ocean on the other.

• A single specialised ship would have to travel enormous distances during an emergency.

• The two-vessel architecture improves: response time;

availability during maintenance; geographic coverage; submarine safety; and operational redundancy.

• When combined with one DSRV system for each seaboard, it creates a much stronger two-coast submarine-rescue architecture.

• Sister ships: Both belong to the same Nistar class and were ordered as part of a two-vessel programme.

• The Navy contracted Hindustan Shipyard Limited for the two DSVs in 2018. Both vessels were launched at Visakhapatnam in 2022.

• INS Nistar: First ship, commissioned in 2025 and assigned to the Eastern Naval Command.

• INS Nipun: Second ship, commissioned in 2026 and strengthening the Western Naval Command.

• Complementary function: Together they provide diving, underwater intervention, salvage and submarine-rescue support across India's maritime areas of interest.

• This is important because it shows that India's submarine-rescue capability is not confined to domestic waters.

• Exercise Pacific Reach: It is a multinational submarine-rescue exercise intended to improve interoperability and procedures among countries operating submarine-rescue systems.

• INS Nistar participated in the 2025 edition hosted by Singapore. India's Submarine Rescue Unit (East) embarked on the vessel and conducted operations in the South China Sea.

• Operational milestone: During the exercise, the Indian DSRV successfully mated with foreign submarines, including a Republic of Korea Navy submarine and Singapore's RSS Invincible.

• Why important: Submarine rescue is inherently international. A disabled submarine may need help from whichever capable rescue force can reach it fastest.

• Interoperability therefore saves lives.

• Public good: Unlike many military capabilities, submarine rescue is inherently cooperative. Countries benefit when neighbouring navies possess compatible rescue systems.

• Regional assistance: The Navy has explicitly stated that INS Nipun can support distressed submarines of partner countries and strengthen India's role as a preferred submarine-rescue partner.

• Maritime diplomacy: Rescue capability can support:

• humanitarian naval cooperation;

confidence-building; joint exercises; interoperability; training partnerships; and India's broader first-responder role in the Indian Ocean.

• This gives INS Nipun a diplomatic significance in addition to its operational military value.

• Blue-water capability: A blue-water navy is broadly one capable of sustaining significant operations far from its home coastline for extended periods.

• Aircraft carriers, destroyers and submarines are the most visible elements, but they cannot operate effectively without support vessels.

• A genuinely deployable navy also requires: fleet tankers;

repair capability; survey vessels; submarine support; diving support; salvage; medical facilities; and rescue infrastructure.

• INS Nipun therefore represents the less visible but essential support architecture of a blue-water navy.

• It expands India's ability to sustain complex underwater operations without relying completely on shore infrastructure.

• Salvage: Naval salvage involves locating, stabilising, recovering or removing damaged, stranded or sunken ships, aircraft, equipment and other objects.

• It may require: divers;

ROVs; underwater cutting; lifting equipment; surveys; pressure-safe operations; and precise ship positioning.

• INS Nipun's diving systems and remotely operated vehicles can therefore support underwater salvage alongside its submarine-rescue duties.

• Salvage capability is valuable after accidents, maritime disasters and defence-related incidents.

• Yes.

• The Ministry of Defence states that INS Nipun can provide specialised support for Humanitarian Assistance and Disaster Relief (HADR) missions in addition to submarine rescue and underwater salvage.

• Potential situations include: recovery after maritime accidents;

search for submerged wreckage; assistance after port disasters; underwater inspection following cyclones or earthquakes; recovery of aircraft or vessels; and support to partner countries.

• Its medical and diving infrastructure provides capabilities unavailable aboard many conventional ships.

• Not merely import substitution: Designing and constructing a specialist DSV requires integration of:

• hull design;

propulsion; navigation; dynamic positioning; electrical systems; life-support systems; diving complexes; ROV handling; cranes; medical systems; and submarine-rescue equipment.

• Therefore, the project develops industrial and engineering knowledge beyond the individual ship.

• Indian builder: Hindustan Shipyard Limited, Visakhapatnam, constructed both Nistar-class vessels. The government reported nearly 75% indigenous content for Nipun.

• Strategic benefits: Domestic construction can improve:

• lifecycle maintenance;

availability of spares; repair autonomy; engineering skills; domestic vendor development; and future naval design capability.

• It also reduces dependence on a foreign supplier for the entire platform.

• No.

• Indigenisation is a spectrum: Indigenous construction of the ship does not necessarily mean that every high-technology sensor, diving component, specialised rescue subsystem or machine originates domestically.

• A 75% indigenous-content figure itself implies continued foreign content.

• Next-stage challenge: India's objective should therefore move from indigenous ship construction towards indigenous capability in:

• diving technology;

underwater robotics; sonar; hyperbaric systems; dynamic positioning; specialist gas-management systems; rescue-submersible technology; and pressure-resistant materials.

• This distinction between platform indigenisation and technology sovereignty is useful in GS3 answers.

• The vessels were designed and built in accordance with the classification rules of the Indian Register of Shipping (IRS).

• Classification society: A classification society develops technical standards for the design, construction and periodic survey of ships and marine structures.

• It verifies whether the vessel meets specified safety and technical requirements.

• For a highly complex DSV, classification is particularly important because underwater diving and pressure-support systems involve high safety risks.

• Extreme environment: Deep-sea pressure, darkness, temperature and currents increase risk.

• Time-sensitive rescue: Submarine accidents leave very little room for delays.

• Specialised manpower: Ships alone are insufficient. India needs trained saturation divers, DSRV pilots, submarine-rescue specialists, diving doctors and ROV operators.

• System reliability: Diving chambers, gas-management systems, rescue vehicles and ROVs must work immediately when required.

• Interoperability: A DSRV may have to mate with a foreign submarine, requiring common rescue standards and regular international exercises.

• Maintenance: Rescue systems are rarely used in real emergencies, so readiness must be preserved through rigorous drills and certification.

• Logistics: A DSRV may have to be transported hundreds or thousands of kilometres before reaching the distressed submarine.

• Therefore, the real measure of submarine-rescue capability is not ownership of sophisticated equipment but the ability to mobilise the entire rescue chain rapidly and reliably.

• Maritime security is often discussed through piracy, sea-lane protection, naval combat and coastal security. But it also includes the ability to keep one's naval forces functioning safely.

• Submarine force assurance: Crews are more operationally confident when credible rescue arrangements exist.

• Readiness: A rescue capability helps protect highly trained personnel and expensive strategic platforms.

• Regional partnerships: Rescue cooperation generates trust even among countries that may not be formal military allies.

• Underwater domain awareness: Sonar, ROVs, diving systems and seabed operations develop wider expertise in understanding the underwater environment.

• Strategic resilience: A navy capable of fighting beneath the sea must also be capable of repairing, rescuing and recovering beneath the sea.

• Primarily an enabling platform: Its main importance lies in support and resilience rather than conventional weapons.

• It does not need to be a frontline combat ship to influence combat effectiveness.

• For example: submarine crews can operate with stronger rescue backup;

damaged underwater equipment can be inspected; underwater repairs can be undertaken; rescue missions can be conducted farther from home; objects can be recovered from deep water; and submarine-rescue cooperation with partners becomes possible.

• Military capability should therefore be understood as an ecosystem rather than simply the number of missiles, aircraft or submarines.

• Geographic scale: The Indian Ocean extends from eastern Africa and West Asia to Southeast Asia and Australia.

• Major sea lanes: Critical global energy and commercial routes pass through the region.

• Growing submarine activity: Regional and extra-regional navies increasingly deploy submarines in these waters.

• India's position: India's location near major sea lanes and its growing naval reach make underwater readiness increasingly important.

• A mobile submarine-rescue capability allows India to contribute a specialised service that relatively few regional states can independently provide.

• This can complement India's larger role as a security and first-response partner in the Indian Ocean.

• INS Nipun illustrates a transition from platform acquisition to capability creation.

• A submarine force is not complete simply because submarines are commissioned.

• It also requires: rescue systems;

diving support; maintenance; training; medical infrastructure; surveillance; seabed intervention; logistics; and operational partnerships.

• Similarly, indigenous naval power is not created merely by assembling ships domestically. It requires a sustained domestic ecosystem capable of designing, building, maintaining and upgrading highly specialised technologies.

• That makes INS Nipun relevant to three major GS3 themes simultaneously: maritime security, defence indigenisation and technological self-reliance.

• Science and technology dimension: Saturation diving, heliox, ROVs, dynamic positioning, hyperbaric systems and DSRVs.

• Defence dimension: Submarine rescue, underwater intervention, salvage and naval readiness.

• Industrial-policy dimension: Indigenous design, Hindustan Shipyard Limited and domestic defence manufacturing.

• International dimension: Submarine-rescue interoperability and assistance to partner navies.

• Strategic dimension: A blue-water navy requires sophisticated support infrastructure, not merely combat platforms.

• Thus, INS Nipun should be studied as an example of how an apparently specialised auxiliary vessel can significantly increase the resilience and reach of a modern navy.

• Maintain round-the-clock rescue readiness: India's two DSRV systems and Nistar-class ships should undergo frequent mobilisation, mating, rescue and medical-response exercises so that the entire rescue chain remains operational.

• Strengthen two-seaboard coverage: INS Nistar and INS Nipun should be integrated closely with the respective submarine rescue units, aviation assets, naval bases and vessels of opportunity to reduce emergency response times.

• Deepen indigenisation: India should gradually localise critical underwater technologies, including ROVs, diving systems, hyperbaric equipment, sensors, positioning systems and future rescue submersibles.

• Develop specialised human capital: Expansion of hardware must be accompanied by more saturation divers, diving doctors, ROV operators, submarine-rescue specialists and underwater engineers.

• Improve international interoperability: Regular exercises with regional and extra-regional navies can ensure that Indian DSRVs can operate effectively with different submarine designs.

• Build regional rescue partnerships: India can institutionalise submarine-rescue cooperation with Indian Ocean partner countries through training, standard operating procedures and joint exercises.

• Advance underwater robotics: Autonomous and remotely operated underwater technologies can reduce risks to human divers and improve inspection, salvage and rescue capability.

• Strengthen domestic shipbuilding supply chains: HSL and Indian suppliers should use experience from the Nistar programme to expand capability in specialist naval vessels and high-value marine systems.

• Integrate civilian disaster-response roles: Where appropriate, deep-sea diving and salvage expertise should be available for major maritime accidents and HADR operations.

• Treat support vessels as core naval assets: Future naval planning should ensure that the growth of submarines and surface combatants is matched by adequate rescue, repair, logistics and specialist support capacity.