China’s enhanced Underwater Domain Awareness (UDA) strategy: A lesson for India and the global community

In the last decade, one has observed repeated and serious attempts by Chinese research vessels to collect data in the Indian Ocean Region (IOR). The year 2018, saw 24 research cruises by Chinese vessels in the IOR, whereas during the same period six other nations, including US, India, France and others, have undertaken only 26 such cruises in the IOR.

Dr (Cdr) Arnab Das Aug 28, 2023
Chinese ships off Colombo port (Photo: UDA Digest)

The global community in the 21st century has increasingly shifted its strategic interest to the Indo-Pacific region. It is important to note that the Indo-Pacific by definition is the tropical waters of the Indian Ocean and the Pacific Ocean. The tropical waters present unique challenges and opportunities; they present rich bio-diversity and thus have significant socio-economic potential. The rich civilizational legacy also translates to the strong bond between the oceans and the sociocultural practices. The traditional knowledge and practices have been robust and sustainable. The massive undersea resources (non-living) comprising rare earth minerals and energy resources make them attractive for economic growth. 

However, the tropical waters also suffer sub-optimal performance of the sonars deployed for any acoustic survey irrespective of the application. The degradation of performance is of the order of 60 per cent; thus asset deployment for the same area coverage is more than six times. It is a no-brainer that the sonars supplied by the West that were designed and developed during the Cold War era for the temperate and polar regions are no good for the tropical waters.

The United States strategic community after a brief phase of denial during the last decade of the last century, acknowledged that the Chinese in the tropical waters of the South China Sea and nearby areas need to be tackled differently. Deployment in tropical waters requires a fundamental shift in the very definition of shallow vs deep waters. The Hypsometric definition used during the Cold War period for shallow (less than 200 m), waters was based on the edge of the continental Shelf. The continental shelf, worldwide extended approximately up to 200 nautical miles from the coast and then there was a sudden fall in the depth. The depth of the water column at the edge of the continental shelf was 200 m. However, acoustically the shallow waters were based on the number of interactions of the acoustic signal with the two boundaries (surface and the bottom), during its propagation in the underwater medium. 

Littoral Anti-Submarine Warfare

The Sound Axis (axis with minimum sound speed) determines the propagation characteristics (Refraction vs Reflection). The depth of the Sound Axis at the poles is 50 m, whereas at the equator is 2000 m, thus in tropical waters the sound axis will not be found even at depths beyond 1500 m. This will result in excessive interaction of the acoustic signal with the surface and bottom, making sure that the sound signal carries the surface and bottom characteristics along, during its propagation journey. This leads to serious distortions of the acoustic signal in the tropical waters compared to the other regions. The temperate and polar waters, allow refraction around the Sound Axis, even at water column depths of less than 500 m, so the propagation losses are minimal. The Littoral Anti-Submarine Warfare (ASW) became a buzzword in the American strategic security discourse in the post-Cold War era. They had to customize their deployments and acoustic processing techniques to mitigate the tropical distortions in the sonar output.

The Americans realized that to counter the Chinese in the tropical waters of the South China Sea (SCS) they had to develop better Underwater Domain Awareness (UDA). The Americans announced what is called the ASIA-EX in early 2000. ASIA-EX was a massive Shallow Water Acoustic Measurement (SWAM) exercise in the South China Sea (SCS) and East China Sea (ECS). The entire project was funded by the Office of Naval Research (ONR). It was led by the University of Washington and five other US Universities, that carried out large-scale Modelling & Simulation (M&S) exercises for the experimental area in the first phase. The M&S had to be followed up with field experimental validation in phase 2. The Americans knew that the field validation in these waters would cause a serious diplomatic backlash, so they included multiple academic institutes from the region including Chinese, Taiwanese, Hong Kong, and others. Approximately 20 institutes, including six American universities, participated in the exercise that continued for over four years and a massive amount of data was collected. The Americans are yet to completely analyze the acoustic data collected during the ASIA-EX and they are seeking Indian help for the same. 

The strategic requirement of the Americans was amply clear and they continued to collect data even post ASIA-EX. The US Navy started deploying Underwater (UW) Drones regularly and any vessel of opportunity passing through the region deployed Acoustic Arrays to collect tropical data. However, the Chinese also participated in the ASIA-EX with all seriousness. The author visited Shanghai in 2016, for the Oceans Conference, considered one of the biggest conferences on the subject worldwide. It was the first time such a conference was being hosted in Mainland China. Interaction with the Chinese experts and strategists revealed that they knew that their classified acoustic data was being taken away by the Americans. However, they also knew that they could have never undertaken such massive-scale SWAMs on their own, so, they participated to learn. 

It was also observed that multiple Chinese researchers from their Navy, National Defence Univesity (NDU), Commission for Science, Technology & Industry for National Defence (CSTIND) and others, regularly went to the University of Washington and other American institutes for higher studies to make sure a serious acoustic capacity & capability building initiative. This effort was seen from the end of the Cold War era.

Underwater Great Wall 

In December 2015, the China State Shipbuilding Corporation (CSSC) announced what was referred to as the “Underwater Great Wall” (UGW). It was part of a focused underwater capacity-building initiative by the Chinese government. The CSSC announced that the UGW is a major project to establish underwater observatories in the disputed South China Sea region. The aim is to build a network of surface and sub-surface sensors for real-time monitoring of maritime targets. The proposed project comprises multiple underwater sensors mounted on surface ships, sonar systems, underwater security equipment, marine oil and gas exploration equipment, unmanned underwater vehicles and marine electronic equipment. The UGW is expected to provide a comprehensive Underwater Domain Awareness (UDA) for surveillance, environmental monitoring, disaster management and undersea exploration/exploitation. 

In January 2016, the Chinese captured an Underwater Drone in the South China Sea. The drone was launched from USS Bowditch, a US Navy survey vessel. The Chinese kept it for three days and when the shouting became loud enough, they released it after the messaging was done, loud & clear. The US president-designate Donald Trump broke protocol to announce that such an act was a challenge to US sovereignty. The entire Trump Presidency saw a massive confrontation between the two navies, in the name of “Freedom of Navigation” in the South China Sea. Figure-1 presents the comparison of the Sound Surveillance System (SOSUS) and the Underwater Great Wall (UGW) locations. 

The SOSUS was the first serious attempt at UDA globally, however, it was for the temperate and polar waters at the peak of the Cold War period. The SOSUS did provide serious inputs for enhancing sonar performance and minimizing the medium impact in the initial days; however, today that is not valid for tropical waters. The West continues to push their hardware developed for the Cold War requirement, to the developing world even in the tropical waters, knowing fully well that it requires massive customizations to suit the local conditions.


China's IOR forays

In the last decade, one has observed repeated and serious attempts by Chinese research vessels to collect data in the Indian Ocean Region (IOR). The year 2018, saw 24 research cruises by Chinese vessels in the IOR, whereas during the same period six other nations, including the US, India, France and others, have undertaken only 26 such cruises in the IOR. It may be important to note that the international community does not have enough data with appropriate resolution to deploy underwater drones in the IOR. 

When the MH-370 (Ill-fated Malaysian Airline that was lost in March 2014) search had to be undertaken in the Southern Indian Ocean, the Underwater Search and Recovery (UWSAR) team, first took almost a year to generate charts of appropriate resolution to deploy Autonomous Underwater Vehicles (AUVs). AUVs, whether for military or non-military purposes will require massive scale UDA with appropriate specifications. Even AUV design and development with appropriate payload and design specification is a highly specialized field and also resource intensive initiative. 

UDA largely has four major stakeholders, namely strategic security (including both internal & external security), blue economy, environment, disaster and climate change risk management and science and technology (digital transformation). The nations in the Indo-Pacific strategic space are largely fragmented both within and in the region. The UDA framework has to encourage pooling of resources and synergizing of efforts across the stakeholders and also among the nations within the region, to ensure effective management of the challenges and opportunities. In the present context, given the political volatility and economic limitations, they are suffering in both situations. 

The extra-regional powers are exploiting the nations in the region, by pushing their hardware at high cost that does not give reasonable outputs and thus the available resources are not able to give them enough returns. The West has done what it had to and now the global regulatory provisions have become extremely prohibitive for the developing nations in the region. Effective UDA will bring transparency and facilitate enhanced governance mechanisms. The digital transformation in the underwater domain will be the only way forward. The digital transformation should map the traditional knowledge and practices to ensure sustainable scaling up, rather than trying to replace them. 

 (The author is Founder-Director of the Pune-based Maritime Research Center. Views are personal. He can be reached at More on the UDA framework are available at

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