Diver detection sonar (DDS) systems are sonar and acoustic location systems employed underwater for the detection of divers and submerged swimmer delivery vehicles (SDVs). The purpose of this type of sonar system is to provide detection, tracking and classification information on underwater threats that could endanger property and lives. Further, this information is useful only to the extent that it is made available to authorities in time to make possible the desired response to the threat, be it deterrent or defensive action. Subsurface threats are a difficult problem, because reliable detection is available to date chiefly by use of high-resolution active sonar or trained dolphins or sea lions. The threat of an underwater terrorist attack is a concern to the maritime industry and port law enforcement agencies. Ports face a range of threats from swimmers, boat-delivered ordnance such as limpet mines and other forms of improvised underwater explosive devices. DDS systems have been developed to provide underwater security for ports, coastal facilities, offshore installations, pipelines and ships. Due to the variety of life and objects that exist under the water, it is desirable that a DDS system be capable of distinguishing between large sea mammals, shoals of fish; a ship's wake; a diver with an open circuit scuba set and a stealth diver with a rebreather. DDS systems have been developed that can be mounted on the seabed, on a pier or on the hull of a vessel. For complete port security these systems are integrated with the surface surveillance and security systems employed at ports, coastal facilities and offshore installations. Various systems provide specialized features to facilitate their use in port security systems including automatic detection features.
In 2006, in a NATO report given by R. T. Kessel and R. D. Hollet at the NATO Undersea Research Center, it was stated that sonar gives by far the lowest cost per square meter of underwater coverage of all other means of surveillance (radar, video, visual). This is because sound waves have a low attenuation and long propagation distance in turbid harbor waters relative to other means of sensing (electromagnetic waves, visual light, temperature, magnetism). The leading sonar technology for detecting and tracking underwater intruders is active, monostatic sonar, using principles of conventional beam forming in its signal processing. These sonars are now available from a number of different manufacturers who recommend their use for surveillance against underwater intruders, whereas, other sonar technologies, such as active multi-static or passive sonar, possibly with model-based signal processing, remain at best in the development stage so far as intruder detection is concerned.
In the above-mentioned study, conducted with the Italian Navy, it was found that diver or intruder detection sonar technology is mature inasmuch as:
In December, 2008, DDS system sold to an undisclosed EMEA government. The system was installed in an area with critical infrastructure, including a port and energy production facilities.
March 4, 2009, a $1.7M order for an underwater security system was placed, to be used by a large energy facility at an undisclosed location in Asia, to guard and protect the customer infrastructure from underwater intrusion and sabotage.
March 12, 2009, sale of multiple DDS sensors, which protect a strategic site against underwater intrusion.
May 25, 2009, US Navy orders additional sonar systems.
December 2011, Asian customer places the world's largest order for underwater security systems protection of oil platforms.
March 2012, undisclosed navy places repeat order for multiple DDS systems.
May 2012, multiple sales of diver/intruder detection sonars for undisclosed middle eastern facilities.
August 2012, ministry of defense of one of the world's largest armies orders a portable diver detection sonar.
November 9, 2012, a large defense integrator places an order for six portable diver detection sonar for vessel protection.
June 2016, armed forces of Kazakhstan order several diver detection sonar for the second time.
January 8, 2018, Indian Navy ordered 78 PointShield portable diver detection sonar units.