Underwater Sonar: Side-Scan Imaging Sonar & Forward Looking Sonar for Obstacle Avoidance & Navigation

The Evolution of Underwater Threats

Feature Article by Wavefront Systems
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Wavefront Systems discusses the growing threat of unmanned platforms in the underwater domain, and the company’s subsequent development of the Sentinel IDS, a portable, lightweight detection system that can be used to detect threats in shallow waters and over a wide range.

The Evolution of Unmanned Underwater Threats

In our globalized world, economic prosperity and growth have always been critically dependent on the use of our oceans and seas. With 96% of goods and products shipped by sea, it’s always been vital that this transport option remains open to us. Therefore, the security of our seas, ports, harbors and offshore facilities, for both governments and companies, remains a high priority.

Criminals and terrorists have always been aware of the difficulty of keeping such large swathes of water safe from their activities and have used it to their advantage. Only a few years ago, the use of a diver to carry out attacks was the main underwater tactic. Deterring and defeating these criminal enterprises is a constant battle but the intelligent use of advanced technology has been one of the key ways to defeat them.

But, for governments and security forces, underwater threats are changing in both their purpose and methodology. Our geopolitical climate has become more volatile, particularly with the ongoing war in Ukraine, and intelligence points towards more attacks of a terrorist nature on our Critical National Infrastructure (CNI).

Are we heading towards a new kind of war?

Threats to navies, high value CNI installations, private maritime assets and political events worldwide are constantly evolving, from new and increasingly sophisticated technologies to more traditional threats that are sometimes harder to detect.

When thinking of drone threats, traditionally you will think of the aerial domain. Countermeasures have been developed to keep pace with a vast range of drone platforms, from small, homemade devices to large, sophisticated UAV platforms. These threats have evolved quickly, and security and defense services have adapted to respond and deploy technologies that protect people and platforms.

Now, we are seeing an increasing threat posed by unmanned platforms in the underwater domain, and this presents an entirely new set of challenges when developing detection systems and countermeasures.

Detecting threats on the surface through above water surveillance can be controlled through several means, including CCTV, FLIR (Forward Looking InfraRed) radar, and access control measures. However, the subsea presents potential foes with a covert environment where visibility, terrain, noise, and naturally occurring fauna, animals, and debris make threat detection and classification a seemingly insurmountable challenge, leaving vessels and crews extremely vulnerable to attacks.

The underwater space is no longer solely the domain of large, manned submarine platforms, and new threats are quickly emerging from autonomous, agile UUVs, bringing an entirely new challenge. Should the development of these UUV platforms reflect even half the pace at which aerial drones evolved, it becomes critical that we are equipped with the technologies and expertise needed to detect, classify and track these threats.

The Evolution of Underwater Threats

The nature of subsea threats

The development of unmanned subsea platforms has moved on significantly, with many academic establishments with a waterfront regularly testing UUV technology with their own software. What we have in the subsea realm now is where we were with air drones ten years ago, but commercial availability is still a way off due to their expense. However, this does not mean that we can ignore the threat. The fact is that these threats will continue to evolve and new subsea platforms will be developed imminently, and countermeasures and detection technologies have to be able to keep pace.

For detection and navigation, the key difference that sets surface and subsea drones apart is GNSS, as the satellite-based navigation system does not work underwater making accurate positioning an issue. Visually you cannot see very far, making it harder to use cameras and radars to see threats in an environment that is difficult to evaluate. The reliable detection of underwater intruders of any form is a notoriously tricky problem. In the case of combat divers for example, the threat is incredibly small and extremely quiet, whereas a UUV is also fast-moving and difficult to track.

Traditional subsea detection technologies rely on acoustics and sonar, however, this becomes incredibly challenging in key strategic areas such as ports and harbors where a number of vessels and crew could be under threat. These areas are some of the noisiest acoustic environments you can find, where multiple, often large, and therefore ‘noisy’ vessels constantly come and go, and depth sounders may be continually active. In addition, the relatively still water creates a complex thermal structure and one where you’re unlikely to be able to rely on a low reverberation seabed. In congested and challenging port and harbor areas, the sound velocity profile will constantly change.

It’s not just detection that presents a challenge. Once a target is detected, it must also be classified and distinguished from marine fauna. Identifying whether a potential threat is a harbor seal, a terrorist diver or UUV is a determination that must be made correctly otherwise the consequences could be dire.

Knowledge is power in underwater security. You can’t react if you don’t know it’s there

New technologies need to apply in-depth technical knowledge and understanding of monitoring to identify, classify, and track a range of new threats. The better the understanding of the threat landscape in the unseen subsea environment, the more protection that can be offered.

As leading global experts in subsea technologies, Wavefront Systems looked to address challenges by bringing a portable, lightweight detection system to market that could be used to detect threats in shallow waters and over a wide range.

As a result, Wavefront Systems developed the Sentinel IDS system, capable of emitting a 360° Linear-Period-Modulated (LPM) pulse and using 256 receive beams equally spaced along a perimeter to detect and discriminate targets at up to 1,500m range. The system is capable of being deployed rapidly in it’s portable format as a stand-alone sonar or can be set up as part of a network of sonars to protect a permanent wide-area perimeter.

Simultaneous Active and Passive sonar capability SInAPS®

It now includes passive detection. The Simultaneous Active and Passive sonar capability SInAPS is Wavefront’s highly innovative approach within Sentinel 2. It combines the very best that both tracking methods have to offer by using the same acoustic array for both active and passive processing, simultaneously within the same operating band. This allows the tracking of discrete and obscured targets that stand-alone active sonars would historically not be able to identify. Thus, leaving the threat nowhere to hide.


Wavefront are applying new technologies, in-depth technical knowledge and an unrivaled understanding of underwater monitoring with the ability to analyze the subsea environment to identify, classify and track a range of new threats keeping assets protected.

Find out more about Sentinel IDS – Underwater Intruder Detection Sonar>

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Posted by Caroline Rees Caroline co-founded Unmanned Systems Technology and has been at the forefront of the business ever since. With a Masters Degree in marketing Caroline has her finger on the pulse of all things unmanned and is committed to showcasing the very latest in unmanned technical innovation. Connect & Contact