China’s expanding oceanographic presence in the Indian Ocean is becoming an increasingly important maritime-security concern. A 2024 study by the Centre for Strategic and International Studies (CSIS) identified 64 Chinese research and survey vessels operating worldwide between 2020 and 2023, including 13 in the Indian Ocean. The study also found that more than 80 per cent displayed indicators of potentially suspicious behaviour or organisational links that could point to broader strategic objectives.
This does not mean that Chinese research missions are inherently military operations. The concern is more subtle: oceanographic data collected for legitimate scientific purposes can also have significant military value.
Seabed contours, currents, temperature, salinity and underwater acoustic conditions can influence submarine navigation, sonar performance and anti-submarine warfare (ASW). As the PLA Navy operates farther from China’s immediate maritime periphery, knowledge of unfamiliar underwater environments becomes increasingly valuable.
India’s response
India’s response is shaped by both security concerns and the legal framework governing foreign research in its maritime zones. Under Article 246 of the United Nations Convention on the Law of the Sea (UNCLOS), marine scientific research in a coastal state's Exclusive Economic Zone generally requires the consent of that state.
This became particularly visible in 2019, when the Indian Navy confronted the Chinese research vessel Shi Yan 1 after it was detected conducting survey activity without the required Indian permission near the Andaman and Nicobar Islands.
The Xiang Yang Hong 03 episode in early 2024 presented a different challenge. India closely monitored the vessel as it sailed towards the Maldives. The case highlighted an important reality: research vessels can operate legally in international waters while collecting information that may still have strategic relevance.
For India, the challenge is therefore not simply determining whether a vessel is operating legally. It is understanding what information is being collected, where it is being collected, and how it might eventually be used.
UFOSS: A proposed fixed underwater layer
Against this backdrop, India’s proposed Underwater Fiber Optic Sensing System (UFOSS) could become an important addition to its underwater-domain awareness architecture.
In July 2026, the Naval Physical and Oceanographic Laboratory (NPOL) of the Defence Research and Development Organisation (DRDO) issued an Expression of Interest for the development and implementation of the system. The proposed architecture includes seabed sensor nodes, subsea fibre-optic cables, junction boxes, branching units and a shore station.
Importantly, UFOSS remains a development and procurement programme, not an operational underwater surveillance network. Its potential significance lies in persistent sensing. Unlike ships and aircraft, which can only patrol an area intermittently, a fixed seabed system could continuously monitor selected approaches and provide early indications of underwater activity.
India already possesses relevant technological expertise. DRDO and NPOL have worked on fibre-optic hydrophone arrays, underwater acoustics, sonar and signal processing. These capabilities could provide a foundation for a larger networked sensing architecture. International experience also demonstrates the potential value of such systems. The United States developed SOSUS during the Cold War and later incorporated fixed and mobile systems into the broader Integrated Undersea Surveillance System.
The lesson is straightforward: fixed sensors are most effective when connected to shore-based processing and integrated with mobile ASW forces.
Pakistan’s submarine modernisation
India’s underwater challenge is not limited to China. Pakistan is also modernising its submarine force through the acquisition of eight Hangor-class submarines from China, including four built in China and four in Pakistan. The class incorporates modern sensors, combat systems and air-independent propulsion intended to increase submerged endurance.
A larger and more capable Pakistani submarine force could increase the number of underwater contacts the Indian Navy must detect, classify and track. This strengthens the case for persistent surveillance. However, fixed sensors cannot replace conventional ASW forces. They may detect or cue a contact, but ships, aircraft and helicopters are still needed to investigate and respond.
India’s layered ASW response
India is increasingly developing a layered ASW capability in which different platforms perform complementary roles.
Garden Reach Shipbuilders & Engineers (GRSE) illustrates this approach. The Kolkata-based shipyard has contributed to several layers of India’s maritime architecture, building or constructing Project 28 ASW corvettes, Project 17A frigates, ASW Shallow Water Craft and Survey Vessel Large ships.
The Project 28 Kamorta-class corvettes, all four built by GRSE, provide a specialised ASW capability. Designed specifically for submarine warfare, they strengthen the Navy’s ability to detect and engage underwater threats, particularly in complex littoral environments.
The Project 17A frigates provide the high-end, multi-mission layer. GRSE has delivered two out of the three P17A ships, with the delivery of the third anytime soon. These frigates combine advanced sensors, combat-management systems, helicopters and weapons for air, surface and subsurface warfare. Their value lies not simply in hunting submarines independently, but in contributing to wider fleet-level ASW operations.
The Arnala-class ASW Shallow Water Craft (ASW-SWC) adds another specialised layer close to the coast. GRSE is building eight of the these vessels. Designed for subsurface surveillance, search and attack missions, these ships combine sonar with lightweight torpedoes and ASW rockets and are particularly suited to shallow-water operations.
The four Survey Vessel Large (SVL) ships delivered by GRSE to the Indian Navy perform a different but equally important role. These ships conduct hydrographic, oceanographic and geophysical surveys, helping build a better understanding of seabed conditions and the underwater environment.
That knowledge matters because effective ASW depends not only on finding submarines, but also on understanding the physical environment in which submarines and sonar systems operate.
From fixed sensors to mobile forces
Taken together, these capabilities point towards an emerging system-of-systems approach.
A future architecture could combine persistent seabed sensing through UFOSS with shore-based processing and information from other surveillance sources. P-8I maritime patrol aircraft and ASW helicopters could provide wide-area search and localisation, while Project 17A frigates, Project 28 corvettes and Arnala-class vessels investigate and respond to contacts.
Survey vessels would contribute environmental and hydrographic knowledge, helping improve the understanding of the underwater battlespace.
In such a network, fixed sensors provide persistence, aircraft provide reach, surface ships provide mobility and weapons, and shore-based systems bring information together.
UFOSS should therefore not be viewed as a system that will make the Indian Ocean “transparent” or automatically detect every submarine. Its real value would lie in persistence, early warning, environmental understanding and sensor fusion.
The larger strategic picture
India’s underwater challenge is no longer simply about acquiring more ASW platforms. It is increasingly about connecting sensors, platforms, data and decision-making into a coherent architecture.
India’s response is gradually taking shape across multiple layers—from hydrographic surveys and proposed seabed sensing to frigates, ASW corvettes, shallow-water craft, maritime patrol aircraft and helicopters.
If these capabilities are successfully integrated, India’s advantage will not come from any single platform. It will come from the network they collectively create.
References:
CSIS — Chinese research/survey vessels in the Indian Ocean
CSIS — Surveying the Seas: China’s Dual-Use Research Operations in the Indian Ocean
UFOSS — July 2026 EOI / seabed fibre-optic network
New Indian Express — India plans seabed cable network to hunt Chinese, Pakistani submarines
Shi Yan 1 — 2019 Indian Navy action
India Today — Navy expels suspected Chinese spy vessel from Indian waters
Xiang Yang Hong 03 — Reuters
Reuters — Maldives visit of Chinese survey ship could rouse Indian Ocean security concerns
Xiang Yang Hong 03 — India monitoring the vessel
Economic Times — Chinese spy vessel headed to Maldives, India keeping a close watch
Xiang Yang Hong 03 — Indian Navy monitoring
Hindustan Times — Navy to monitor Chinese ship in Indian Ocean headed to Maldives
(Rahul Sarkar is a DGM (Electrical Design) at GRSE, specializing in naval automation, Integrated Platform Management Systems (IPMS), propulsion control systems. With nearly two decades of experience supporting Indian Navy and Coast Guard programs, his interests include unmanned surface and underwater systems, intelligent ship control, and future naval warfare.)
