The Promise and Pitfalls of Underwater Domain Awareness

Indian Diver.jpg

Few expressions in the maritime lexicon today are as persistent and pervasive as maritime domain awareness. The term has become a watchword in security and governance debates, a conceptual idiom implying information superiority in the nautical arena. Within the greater scope of maritime domain awareness, however, underwater domain awareness is a new and emerging concept that has piqued the interest of maritime analysts. It rests on the idea that modern-day technology has rendered the sea transparent, making it possible for maritime agencies to track undersea activity. The concept is popular among strategic experts, especially in India, where many believe that the game of undersea cat-and-mouse is always afoot in the sensitive littorals and that the adversary is constantly seeking ways to outflank and outmaneuver the defender. Aside from traditional security concerns, maritime theorists also draw attention to undersea geophysical and ecological phenomena that have a negative impact on humans. Improving domain awareness under the seas, they contend, is a way of minimizing the impact of naturally occurring destructive forces.

Underwater domain awareness, however, is inherently hard. It has so far relied largely on the effective use of shipborne sensors, but the latter is limited in range, and their suitability for detecting threats in the noisy and congested littorals has been inconsistent. In recent years, undersea installations and autonomous vessels outfitted with advanced sensors have given mariners a better understanding of the threats in the deep. That endeavor, too, is costly and time-consuming, and the resulting picture is far from complete. In recent years, the advancement of marine robotics has provided some hope for combating the forces that lurk beneath the sea. This has also so far failed to deliver on its promise.

In short, underwater domain awareness is not the strategic game-changer that many anticipate. The technologies that underpin the concept are in the early stages of development, and naval planners are still grappling with its myriad dimensions and challenges. Despite the rhetoric surrounding the concept, particularly in India, underwater domain awareness remains a work in progress at best and an untested proposition at worst, with little clarity on the methods and means of implementation. Rather than putting too much faith in an unproven concept, the Indian navy should seek greater cooperation with partner navies, particularly the U.S. Navy, to reap some of the same benefits in the Indian Ocean.

A Complex Endeavor

The key reality about underwater domain awareness is that it is fundamentally different from “domain awareness” over the seas. The undersea arena is essentially an opaque environment with no well-organized path between the transmission source and the target. Undersea networks rely on sound-wave propagation, which does not follow straight lines, as opposed to over-the-sea atmospheric sensors, which rely on electromagnetic wave transmission. Unlike atmospheric sensors, which operate largely independently of the air medium and cover a large area, acoustic systems are highly dependent on the density and temperature of the seawater, with high attenuation and absorption limiting range and endurance. There are also gaps in the sensor networks that prevent smooth communication between sender and receiver, adding another layer of complexity.



Sonar is the only reliable system of submarine detection in an underwater environment because it processes acoustic information that is either radiated by underwater noise sources of interest (passive sonar) or reflected from underwater objects of interest (active sonar). Both approaches have performance limitations, not least because the platforms that deploy them are restricted in numbers and capability. Sonars need also to contend with the constraints of the platforms deploying them, and a complex ocean environment.

The Anti-Submarine Warfare Challenge

To be sure, underwater surveillance and anti-submarine warfare are two of the most studied aspects of naval operations. The aim in a typical antisubmarine warfare scenario is to locate an enemy submarine while maneuvering to evade detection. But the problem has a dynamic and challenging nature that often ends up revealing the defender’s location. The most dependable method that does not give away the surveillance platform’s position is the use of passive sensors, such as sonobuoys deployed from maritime patrol aircraft and helicopters. Modern navies also use towed array systems and fixed installations of hydrophones such as integrated undersea surveillance system networks to listen for the distinctive noises generated by targets in the ocean. Despite being the preferred method of detecting submarines, passive antisubmarine warfare, however, is limited by low target signatures and high ambient-noise levels.

The other way to detect enemy submarines is by using active sensors, either by deploying transmitting sonobuoys or by deploying hull-mounted and variable depth sonars from surface ships in conjunction with towed arrays and dipping sonar from helicopters. The use of active sensors, however, is tricky. The main problem here is that the parent platform’s deployment profile imposes operational constraints on transmissions. Maritime patrol aircraft and helicopters have limited time on station and cannot provide continuous surveillance; and conventional submarines are unable to be closely integrated into task-force operations due to the need to surface periodically to charge their batteries. Radiated noise from ships deploying sonars and towed arrays places restrictions on the use of active sensors.

Non-Acoustic Sensors 

More recently, other non-acoustic technologies to monitor and sense submarine activity have been developed, including blue-green laser, magnetic anomaly detection, and satellite wake detection. These represent both an opportunity and a challenge. With signal processing becoming cheaper and more affordable, non-acoustic means of antisubmarine warfare are more viable than in the past. However old limitations, particularly the inability of sensors to deal with low signal strength, continue to plague the submarine-detection enterprise. As submarine operations have shifted from “blue water” to the shallower and far more acoustically challenging littorals, and as diesel-electric submarines have become quieter than earlier, the use of non-acoustic sensors has proven to be complicated.

Some argue that bathymetric light detection and ranging has the potential to improve antisubmarine warfare in shallow and congested waters. This is, indeed, a powerful active detection technique for underwater targets that uses blue-green laser transmission characteristics through the fluctuating sea surface to enable long-distance, high-speed communications. However, the technique is limited by the geometry of the sea surface, as well as complex environmental factors such as wind and waves, which have a significant impact on blue-green laser communication performance.

Recently, many analysts and practitioners have come to believe that the magnetic anomaly detector is a sure way of hunting submarines. Magnetic sensors are unquestionably effective in detecting shallow, submerged submarines. However, their performance is often inconsistent, and they are known to be ineffective in locating deep-diving submarines. This is because magnetic detection varies greatly depending on sea conditions, sensor platform speed, and geomagnetic and geological noise. Ongoing efforts to reduce submarine magnetic signatures (by running currents through the hull and using non-magnetic hull materials) have rendered magnetic sensors less effective than previously thought. The Russian navy and the People’s Liberation Army Navy — two major submarine operating navies in the Indo-Pacific region — have even resorted to the use of non-magnetic titanium and the creation of demagnetization facilities respectively as ways of improving submarine stealth. 

The preceding is not meant to minimize the effectiveness of undersea surveillance. Modern commercial tools and technology advancements have certainly broadened the possibilities for locating submarines. Open-source researchers can now better understand the size and composition of countries’ submarine fleets, as well as monitor the construction of submarines and submarine bases. Maritime observers can even detect submarine patrol patterns at sea using commercial satellite imagery and synthetic aperture radar. Even so, submarine detection remains in and of itself a difficult task. With all the tools at their disposal, submarine seekers are only as good at locating submarines, as the available intelligence. 

Underwater Drones

Some maritime observers believe that long-range autonomous underwater vehicles are the answer to the deep surveillance problem. Unmanned or remotely controlled drones can be deployed in forward locations to conduct investigative missions, allowing maritime operations to extend into the adversary’s anti-access/area-denial spaces. Such platforms are effective in carrying out offensive missions, because they can be deployed without endangering the crew of the mothership. They can also be used in large numbers; a swarm of drones can overwhelm target systems and sensors, reducing the opponent’s combat efficiency.



Undersea drones, however, are not a panacea. While potentially lifesaving in emergency situations, such platforms are difficult to deploy and operate. The ships that transport them must be watertight, corrosion-resistant, and capable of withstanding increasing pressures. They must also have adequate lifting equipment and redundancy for launch and recovery operations. In challenging ocean conditions, that is a difficult proposition.

The cost of underwater operations is another constraint. Deploying autonomous undersea platforms necessitates accepting the premise that in the event of a failure, the asset will most likely be lost forever. To avoid inadvertent loss at sea, the ship’s crew must practice deployment, docking, and recharging, all of which can add costs with uncertain returns on investment. There’s also the issue of underwater navigation to consider. Navigating undersea drones in unconfined environments (beyond the coverage of acoustic transponder networks) is challenging — the only reliable method is terrain-based navigation, but it requires accurate maps, which are not always available.

Indian Advocacy of Underwater Domain Awareness

As a conceptual proposition, underwater domain awareness has substantial currency in India. Indian analysts advocate for a comprehensive framework that integrates stakeholders from across the maritime spectrum, such as security agencies, environmental regulators, disaster management authorities, and technology providers. By pooling resources and coordinating efforts, India, Indian scholars and practitioners say, is well placed to harnessed the underwater domain extensively for military as well as civil use. 

Nonetheless, operationally, Indian planners seem unprepared to implement the measures needed to achieve underseas awareness. While the Indian navy has taken steps to defend against attacks in major naval harbors by installing underwater defense and surveillance systems, questions around effectiveness remain. It is unclear if Indian engineers have overcome the challenges posed by limited bandwidth and data capacity in an aquatic environment, and whether the Indian equipment being developed has achieved design maturity and ruggedization for field use. India’s Naval Physical and Oceanographic Laboratory has been pushing for expertise in signal processing, electronic packaging, and materials technology, but is reportedly yet to produce a viable design for seabed sensors. 

With undersea drones, too, there are doubts about whether India’s naval managers have a workable plan. Notwithstanding the Indian navy’s announcement of an “unmanned roadmap” in 2021, India’s Defence Research and Development Organization appears to still be struggling to integrate heterogeneous subsystems in ways that would allow underwater drones to navigate autonomously over long distances. Despite efforts by Indian research agencies to develop new methodologies for the deployment of long-range undersea drones, the systems themselves — Larsen and Toubro’s Amogh, Adamya, and Maya, and the larger underwater-launched autonomous underwater vehicles — remain at the prototype stage. Indian plans to acquire high-endurance autonomous underwater vehicles for antisubmarine operations appear also to be in the early stages. 

Even the seemingly straightforward application of undersea drones for anti-mining is more complicated than many Indian observers believe. Mines, unlike submarines, are usually stationary and require the use of some sort of active detection system like lasers or high-frequency sonar. The Indian navy, which does not currently have any minesweepers in service, worry that submarines from Pakistan or China could infiltrate Indian waters, silently deploying mines. The Indian navy has sought  portable underwater vehicles capable of destroying explosive ordnance as a way of deterring adversarial incursions. However, it remains unknown which active systems these platforms will use for mine-detection. Indian planners prefer a combination of hands-on operator control and automated waypoint navigation, but the latter technology is complex and could complicate the procurement process for foreign-made autonomous underwater vehicles.

Deep-Sea Digital Infrastructure

Another critical issue that proponents of underwater domain awareness appear to have overlooked is the protection of deep-sea digital infrastructure. Submarine cables run beneath the oceans, connecting continents and islands to the internet. This digital infrastructure is threatened by terrorism as well as by fishing, shipping, and natural disasters such as cyclones and tsunamis. The Nord Stream attacks in the Baltic Sea in September 2022 highlighted the vulnerability of undersea infrastructure. 

It is unclear whether the Indian interpretation of underwater awareness considers the possibility of a terrorist attack on undersea infrastructure. For some time, India has been rumored to be planning the installation of high-tech ocean-floor sensors around the Andaman and Nicobar Islands. According to a media report in April 2020, the U.S.-Japan “fish-hook” sound surveillance sensor chain has been extended all the way up to the Andaman-Nicobar Islands, forming a sort of counter-wall against Chinese submarines in the eastern Indian Ocean and South China Sea. There is little evidence to back this claim. What is known is that an undersea fiber cable link between Port Blair and Chennai has been providing internet connectivity since August 2020. Even so, there seems to be no plan in place to protect India’s submarine cables in landing zones along the coast. Submarine communications cables landing in India have yet to be integrated into the country’s critical information infrastructure system. More worryingly, no specialized agency has yet been tasked with safeguarding India’s underwater infrastructure.

A Skeptical Lens

For all these reasons, underwater domain awareness is still a long way from living up to its promise. Rather than putting too much faith in it, Indian planners would be better served by expanding their underseas defense efforts in concert with partner navies, in particular the U.S. Navy. India-U.S. collaboration in the Indian Ocean is already strong, thanks in part to robust defence technology cooperation between the two countries. Since November 2019, when the Indian navy leased two MQ-9 Guardian drones, New Delhi and Washington have explored ways of developing a comprehensive maritime security picture for the Indian Ocean. Indian officials have been negotiating with their U.S. counterparts for the purchase of 30 armed Predator drones for the Indian military. With its share of the drones acquired from the United States, the Indian navy intends to improve underwater domain awareness in the Andaman Sea and the Bay of Bengal. It has already been discussing ways to improve situational awareness under the sea and expand the range of underwater vision with the U.S. Navy and other like-minded partners, such as the French navy. While the United States has, in the past, had reservations about sharing sensitive underwater technology, there remains ground for cautious optimism. 

Indian efforts to expand underwater awareness should go beyond simply trying to see further. They must be aimed at developing better confidence and persistence in what one can observe in the surroundings, as the nature of “seeing” in the undersea arena is different than in other domains. The principal requirement for nations and navies is the development of underwater surveillance tools that can function effectively in a congested marine environment. Multilateral collaboration enables partners to leverage each other’s strengths and capabilities. Only an Indo-Pacific alliance of like-minded players can help underwater domain awareness realize its much touted but still elusive promise as a strategic force multiplier.



Abhijit Singh is head of the Maritime Policy Initiative at the Observer Research Foundation in New Delhi, and a former Indian naval officer.

Image: U.S. Navy combat camera photo by Mass Communication Specialist 1st Class Charles E. White