An oceanic task

Research suggests that most submarine cable disruptions result from accidental damage caused by fishing activities, ship anchors, equipment failures and natural events such as earthquakes. However, the security implications cannot be ignored as deliberate interference can be difficult to distinguish from accidental damage.

India faces three key challenges: monitoring undersea cables to detect disruptions, ensuring coordination among government agencies and private operators, and mobilising repair vessels and spare equipment promptly, which the country lacks at present.

India’s submarine cables are currently concentrated in Mumbai and Chennai, with other landing stations in Kochi, Thiruvananthapuram and Tuticorin, providing connectivity to Southeast Asia. According to a reply by the Ministry of Electronics and Information Technology in the Lok Sabha in March, four submarine cable systems are being commissioned and three more are in the planning stage. Five of these seven systems are expected to join Mumbai’s existing cable landing cluster, increasing the need to strengthen their security.

The question is who bears responsibility when an undersea cable is damaged, particularly if the incident has security implications. Cable operators or telecom companies can detect disruptions and arrange repairs, but they cannot independently investigate every suspicious vessel or secure the regulatory clearances needed to deploy a repair ship in a sensitive maritime area. 

The navy and coast guard are responsible for maritime surveillance, but protecting undersea cables is not necessarily a primary responsibility of either force.

Submarine fibre-optic cables carry 95 to 99 per cent of intercontinental internet traffic, connecting countries and supporting data transmission for banks, software companies, cloud services and other businesses. Stretching thousands of km along shipping routes, these cables are among the cheapest and most efficient means of transmitting large volumes of data between continents. They offer significantly greater capacity than satellites at a lower cost per unit of data.

“The services sector accounts for nearly 40 per cent of India’s exports by value. Our software and IT companies, as well as the financial sector, are entirely dependent on the internet. This makes undersea cables critical infrastructure for the country,” said Admiral R Hari Kumar, former chief of the naval staff.

The network is unevenly distributed along India’s 11,098.81-km coastline. In 2010, a United Nations document described submarine communications cables as “critical communications infrastructure” and “vitally important to the global economy and the national security of all states”. 

A cable landing station (CLS) is an onshore facility where a submarine cable connects to terrestrial telecommunications networks. These stations serve as vital links between international submarine cables and domestic networks. While damage at sea can disrupt a cable system, damage or interference at a landing station can also threaten connectivity. 

“Concentration is a major issue. Out of our 18 cables, around 13 land along a six-km stretch of beach at Versova, Mumbai. That leaves only five dispersed across other cable landing stations. This concentration creates a significant vulnerability,” said Rear Admiral Monty Khanna (retired), Indian Navy.

The concentration of cables does not necessarily mean that a disruption would bring internet services to a halt, as networks are designed to reroute traffic through alternative cables and routes. Nor is this concentration unique to India. In Brazil, around 90 per cent of submarine cables land in the coastal city of Fortaleza, creating a concentration similar to that in Mumbai.

Brazil has taken a more proactive approach, with its navy, army, port authorities and cable operators conducting regular joint exercises. “The objective is to ensure everybody knows that infrastructure belongs to the country, that it’s part of the sovereign critical infrastructure,” said Rui Faria, executive board member of state-backed cable operator Angola Cables.

“It is not enough to have more cables if the new ones continue to land at the same locations. We need dispersal across peninsular India, both to provide redundancy and to increase resilience” said Khanna.

Known as redundancy, this involves having alternative capacity available when part of a network fails. While new cables landing at existing hubs may increase capacity, they offer less geographical protection than cables landing at different locations.

“A big-ticket change could come from Google’s planned cable landing in Visakhapatnam. This would give us a new cable landing location rather than adding to the existing concentration. ,” Khanna said. He added that incentives might be needed to encourage operators to establish landing stations away from existing clusters.

However, diversifying cable landing points is not straightforward. New locations require investment in landing infrastructure, domestic connectivity and the submarine cable systems themselves. These costs compel operators to assess whether a new route has sufficient commercial demand.

The risks extend beyond India’s coastline to international cables passing through maritime regions where multiple networks depend on the same routes. A disruption in the Red Sea, for instance, could affect connectivity between Asia, Europe and parts of West Asia.

A study by the International Institute for Strategic Studies (IISS) on submarine cables in the Indo-Pacific region highlights how planned routes are changing the geography of undersea connectivity. These routes extend into areas that may be less important for conventional shipping but are becoming significant for international communications. 

“We are no longer talking only about protecting existing cables or making them more resilient. New routes and underwater geographies are emerging, adding another dimension to the debate,” said Darshana Baruah, senior fellow for Indo-Pacific Defence and Strategy at IISS. 

“Traditionally, submarine cables have followed routes similar to shipping lanes. But we are now seeing cables being laid in areas that are remote from conventional shipping routes but are becoming crowded with submarine cables. That is the geographical shift,” she added.

The significance of these routes is not always apparent from maps of maritime chokepoints. The Bab el-Mandeb Strait, the Strait of Hormuz and the South China Sea present different challenges, but each illustrates how connectivity can be vulnerable to developments in contested waters.

“Chokepoints expose a number of cables within a limited geography, making them vulnerable. But they also connect so many different countries that it becomes difficult for an adversary to disrupt one cable and affect only one country,” said Baruah.

A cable disruption need not be targeted at India to affect its connectivity. International internet traffic passes through multiple cable systems before reaching its destination. A disruption elsewhere in the network could reduce available capacity, increase latency or force operators to reroute traffic over longer distances.

Ranjan Banerjee, cofounder of Lightstorm, a Gurugram-based digital infrastructure company providing connectivity and network services, said resilience depends on diversifying routes rather than simply adding more cables.

“The real test is whether a single event can take everything out at once. Separate landing points limit the impact of a local incident, while diverse subsea and terrestrial routes provide alternatives for rerouting traffic, provided sufficient capacity is available,” Banerjee said. 

The concentration of submarine cables must also be viewed against growing demand. As data centres, cloud services and digital businesses expand in India, the need for international bandwidth is expected to rise. Yet India has only 17 submarine cables — compared with Singapore’s 28, the highest in Southeast Asia — despite having a much larger population and a growing digital economy.

According to estimates by the United States (US)-based telecommunications research and data company TeleGeography, the US has 113 submarine cable systems, followed by the United Kingdom (64), Japan (45), France (34), Australia (30), China (20), and Germany (10). 

Dattesh Parulekar, assistant professor at the School of International and Area Studies, Goa University, said the geographical concentration of submarine cables could magnify the impact of a targeted attack, causing damage disproportionate to the effort involved.

“The strong concentration of bandwidth-carrying capacity within a small sliver poses critical challenges at multiple levels,” Parulekar said, warning that an attack could disable a “debilitating proportion of critical infrastructure”.

A cable outage begins as a network connectivity problem. The operator detects the fault, identifies the affected system and assesses whether traffic can be diverted through alternative routes. If the cable is damaged, a specialised repair vessel must be mobilised.

While rerouting traffic can minimise immediate disruption, it does not restore the damaged cable. The network may also have less spare capacity until repairs are completed. This makes the availability of specialised repair vessels, along with swift coordination with Indian authorities, critical to restoring connectivity.

India currently lacks a dedicated domestic submarine cable-repair vessel that can be deployed independently when a cable is damaged. Operators instead rely on international maintenance organisations based in the United Arab Emirates (UAE) and Singapore. 

In its 2023 recommendations, the Telecom Regulatory Authority of India (Trai) cited average vessel response times of three to five months from the UAE and four to five months from Singapore and Indonesia. The delays were attributed to vessel availability, spare equipment and regulatory clearances from various government agencies, including the ministries of home affairs and defence.

Submarine cable systems generally follow two ownership models: private ownership by a single operator and consortium ownership shared by multiple operators. The owner or consortium is responsible for arranging repairs using specialised vessels.

Timely clearances, permissions and access to spare equipment can help minimise delays. 

In its 2023 report, “Recommendations on Licensing Framework and Regulatory Mechanism for Submarine Cable Landing in India”, Trai highlighted the challenges of repairing damaged cables. It requires specialised vessels, trained crews and equipment that may not be readily available in India. At present, India does not have such facility.

The report also noted that mobilising vessels from abroad could add 10 to 12 days of transit time for a round trip— with further delays if the vessel is engaged elsewhere — spare equipment is unavailable or government clearances are needed. Foreign crew members might also require security approvals before working in Indian waters.

The International Advisory Body on Submarine Cable Resilience, established in 2024 by the International Telecommunication Union and the International Cable Protection Committee, adopted its final report in Geneva in July. According to the report, around 70 vessels worldwide are capable of repairing submarine cables, but only 20 to 25 are chartered for such work.

“Even if you have a standing agreement with a maintenance organisation, it must have a ship readily available. The ship then has to travel the distance to reach the location where the fault has occurred,” Khanna said.

The time required to arrange a repair can exceed the time needed to carry it out. Once a repair vessel reaches the fault location, its crew retrieves the damaged cable from the seabed, repairs it and lowers it back into position. The process requires specialised equipment, and its duration depends on the depth and nature of the damage.

“Even after a repair ship becomes available, there are other requirements. Customs clearance, personnel clearances and regulatory procedures have to be completed. Depending on where the cable is damaged, different requirements may apply, including the necessity for [Department of Telecommunications (DoT)] personnel to be on board,” Khanna added.

“The repair job itself may take around five to seven days, but the entire process can take three to five months. Your cable remains down throughout that period,” he said, adding that it further adds strain to infrastructure.

The availability of spare cables and equipment is another important factor. The nearest such facility is a submarine cable depot in Galle, Sri Lanka, which stores spare cables, tools and testing equipment needed for repairs.

“One option is for cable operators in India to form a consortium located within the country that can undertake cable repair. This would help in reducing the time taken to respond to a cable fault,” said Khanna, who argued that Indian cable operators could pool resources with neighbouring countries, including Sri Lanka, Bangladesh and Mauritius, to reduce response times.

Khanna explained that a regional arrangement involving neighbouring countries could also share a repair vessel that could serve several markets, making it easier to justify the cost than a ship dedicated to only national networks.

Soham Agarwal, senior fellow at the New Delhi-based National Maritime Foundation, said India’s need for a dedicated repair vessel must be weighed against the cost of keeping it operational. “We need to consider what happens to a repair vessel during periods of downtime. India requires, on average, six to seven repairs a year, but the commercial case becomes difficult if the vessel remains idle for the rest of the time.”

Agarwal suggested that the government and industry work out a viable arrangement rather than assume that the state must own and operate the vessel. A commercial operator could provide repair services to cable systems in India and abroad, while government support could help meet the initial investment costs or mitigate the risk of insufficient demand. “The government could provide viability-gap funding, but it would need to assess how much support is required and how much public money should be used to establish the capability.”

Admiral Kumar also called for India to develop its own submarine cable repair capability through a government-funded vessel operated by a specialised agency. “We need to have our own sovereign capability for cable repair. I would say cable-laying capability as well, so that we can independently lay or repair cables whenever required.”

He suggested that the ministry concerned could fund the vessel and equipment, while an established government organisation could operate them. However, he stressed greater urgency on repair capability than on cable laying. “I would say repairing cables is more important than laying them.”

However, the question is far beyond ownership as India would need trained crew, equipment, spare parts, maintenance arrangements  and a system to prioritise repairs when multiple cables are damaged.

Faria of Angola Cables highlighted a broader challenge: the ageing fleet of cable-repair vessels. “Everybody in this industry recognises that we have a very old fleet that has not been renewed in the last 20 to 25 years,” he said.

A regional fleet could improve the availability of repair vessels, but would require cooperation between governments and the private companies that own and operate submarine cable systems. This raises the question of who should coordinate the response.

Kumar called for a lead coordinating agency without adding another layer of bureaucracy. “We already have a National Maritime Security Coordinator. We could have a subcommittee specifically for undersea cables under that framework. There is definitely a need for a coordination committee, and the lead agency can be decided depending on the area of operation,” he said.

Other experts expressed similar concerns about the lack of a clearly designated national agency to coordinate responses to submarine cable incidents.

“I don’t know if India has a strategy at the national level on who would be the nodal point to respond. There are a lot of issues in the maritime domain that India deals with, but there is no coordinating agency,” Baruah said.

The Indian Navy and Coast Guard have distinct maritime responsibilities, but coordination can become difficult when it falls outside their jurisdiction and  no established mechanism is present.

V S Pathania, former director general of the Indian Coast Guard, said cable protection is not a primary responsibility of the force.

 “Undersea cables are generally marked on nautical charts, so ships are expected to keep clear of them. Protecting these cables is not a primary responsibility of the coast guard, and we do not monitor them on a regular basis. If there is any damage or danger, we receive information about it. Coordination with the navy and other agencies takes place on a case-by-case basis.” 

The industry also has a role in facilitating repairs.

Lightstorm’s Banerjee said India’s reliance on specialised repair vessels adds to delays, as operators have to compete for a limited pool of ships. He said DoT had initiated discussions with the industry and the Directorate General of Shipping on developing domestic repair capabilities and was working towards a single-window mechanism for repair clearances.

“Indian-owned vessels and domestic repair capability would make a real difference, backed by trained crews, spare cables and streamlined permissions,” Banerjee said, adding that the investment would be “best pursued as a shared effort between government and industry”.

The 2008 disruption was not an isolated incident. In February 2024, Iran-backed Houthi rebels in Yemen attacked the MV Rubymar, a UK-owned, Belize-flagged cargo ship, with anti-ship ballistic missiles as it sailed through the Bab el-Mandeb Strait. This forced the crew to abandon the vessel and drop anchor, affecting three submarine cables. The incident highlighted how conflicts involving non-state actors could threaten critical undersea infrastructure.

The ship, which sank after two weeks, forced telecom operators -including those serving India - to reroute data traffic affecting connectivity and internet speed in Europe and other regions.

During geopolitical tension, damage to these cables raises additional security concerns, as it can be difficult to establish whether a disruption was accidental or deliberate. “That is where it falls within the domain of hybrid warfare or grey-zone operations,” Kumar explained.

Grey-zone operations involve actions intended to pressure or disrupt another country without triggering open armed conflict. Identifying such activities underwater is particularly challenging because the vessels involved may also be used for legitimate commercial or scientific purposes.

Other experts also acknowledged the difficulty of conclusively establishing intent in every case. “The issue with grey-zone activity and dual-use capabilities is that you cannot always establish whether something was done intentionally, though it could have been,” Baruah said.

“The subtle sophistication with which such dystopian machination can be carried out further allows plausible deniability to the perpetrator, even as it wreaks havoc in terms of multi-sector disruption on the target country,” Parulekar said. He added that the threat extended beyond physical damage.

In March 2025, the South China Morning Post reported on a Chinese research effort involving a device designed to cut armoured submarine cables at depths of up to 4,000 metres. While the report highlighted a potential capability, it did not establish that the device had been used to sabotage cables or link any specific outage to state-sponsored activity.

Repair equipment, remotely operated vehicles and underwater survey systems have legitimate uses, but some can also be adapted to interfere with cables. Hydrographic surveys can map the seabed and collect data on depth, temperature and salinity. While such information supports scientific research and commercial activities, it can also help militaries better understand the underwater environment.

Baruah said underwater data also has strategic implications. China has extensive experience operating in parts of the Pacific Ocean, while the Indian Ocean presents a different operating environment, where India has considerable regional knowledge.

In February 2025, Taiwan detained the Hong Tai 58, a Togo-flagged vessel with a Chinese crew, after a submarine cable was damaged. The incident highlighted the difficulty of determining whether such damage was accidental or deliberate.

Baruah said that, in prosecuting the vessel’s captain, Taiwanese authorities argued that commercial ships’ navigation systems display the locations of submarine cables, making it harder for a vessel that damages one to claim the incident was accidental.

Vessels may also switch off their automatic identification system (AIS), which broadcasts their identity and position, or transmit misleading information. Such vessels are said to have “gone dark”, although this does not necessarily establish their involvement in sabotage.

Rear Admiral Khanna said maritime information centres help monitor shipping activity across the Indian Ocean. Data from the AIS can be combined with satellite imagery and other surveillance inputs to identify vessels movements requiring further investigation. Given the vast maritime area, the challenge is to narrow down the number of vessels requiring scrutiny and establish whether there is evidence of suspicious activity.

“If a ship switches off its transponder or AIS, it effectively goes dark. You may not know that it is there at all through the normal tracking system, so you have to use other means to establish its presence,” Khanna said, adding that a maritime monitoring centre operates in Gurugram, Haryana.

Advances in technology have also prompted consideration of a similar approach to underwater monitoring. Distributed acoustic sensing, which uses optical fibres to detect vibrations and disturbances along a cable, could help identify the acoustic signatures of vessels and submarines.

It works by sending light pulses through an optical fibre and analysing the signals that return. Changes in these signals, caused by nearby activity, can help identify the location and timing of a disturbance. This could help detect activity near a submarine cable, although the technology’s capabilities and coverage vary. 

However, experts cautioned that the technology is still evolving and could not replace conventional surveillance. While it could alert operators, authorities would still need to establish its cause and determine the appropriate response.

The technology also raises questions about who should control and share sensitive information generated by privately owned cable systems. Sharing such data with maritime security agencies could help detect suspicious activity at sea. However, clear rules would be needed to determine what information operators could share with the government and how authorities could use it.

The United Nations Convention on the Law of the Sea (Unclos) contains provisions governing submarine cables, including requirements for states to make certain forms of cable damage punishable under national law. Article 113 of Unclos covers damage to submarine cables on the high seas, whether caused intentionally or through negligence.

Legal accountability depends on where the damage occurs, the vessel’s flag state and the applicable national laws. On the high seas, affected countries face challenges in identifying and prosecuting those responsible, while their authority to board foreign vessels is legally restricted. 

Agarwal highlighted these jurisdictional gaps, while Khanna argued that existing regulations had not kept pace with the growing importance of submarine cables.

“The existing framework is weak because these provisions were written at a time when telegraph cables were being used. Those cables were important for communications, but they were nowhere near as important as undersea cables are today,” Khanna said.

Revising international rules would require agreement among countries, a process that could take time. However, experts said countries could strengthen domestic laws, improve

information-sharing and use diplomatic channels to seek explanations when cable damage occurs.

For India, the challenge goes beyond investigating individual incidents. The country must identify vulnerable routes, assess how much traffic can be rerouted if a region becomes inaccessible and determine whether alternative routes have sufficient capacity to maintain essential services.

In the event of a severe outage, the government and industry may need mechanisms to prioritise essential communications over less critical, high-bandwidth traffic. Satellite connectivity could provide an alternative for some services, although it cannot match the capacity of submarine cables. Such arrangements would also require clear regulations governing data security, lawful access and government oversight of foreign satellite networks.

Starlink, which has been seeking to enter the Indian market since 2022, has secured key licences but is awaiting final approvals, including security and foreign investment clearances. Eutelsat OneWeb, backed by Bharti Airtel, and Reliance Jio are also awaiting security clearances.

None of these measures can eliminate the risk of submarine cable damage. Nor can India prevent every incident in international waters. Protecting these cables, therefore, requires a coordinated national response rather than leaving responsibility solely to telecom operators or maritime security agencies.

Undersea cables may be out of sight, but responsibility for protecting them cannot remain out of view.