Diver Detection and Deterrence: Navy, Coast Guard Collaborate To Defeat the Underwater Threat

by Joseph DiRenzo iii and Christopher Doane
By Joseph DiRenzo III, and Christopher Doane, Even before the disruption this summer of a major terrorist plot to use in-flight mixtures of liquid explosives to destroy 10 or more passenger aircraft en route from London’s Heathrow Airport to various U.S. destinations, American and allied law-enforcement officials and first responders were analyzing a broad spectrum of other hazards and threats to economic and population centers around the world. One area of renewed interest – which received a splash of publicity a few years ago in various newspapers and magazines but has been largely ignored since – is what officials describe as “the underwater battle space.” In his book, A Time Bomb for Global Trade, Michael Richardson gave special attention to the subject, which usually has a relatively low budget priority. “Anti-Terrorism investigators worry that divers trained by Al-Qaeda or its affiliates,” Richardson pointed out, “could plant explosives on the hulls of ships, act as seagoing suicide bombers, or sneak aboard vessels and commandeer them for attacks.” His comments were reinforced by former CIA Director George Tenet. In February 2003, testifying before the U.S. Senate Committee on Intelligence, Tenet noted that one area of major concern to U.S. security experts is the potential use of “underwater methods” to attack maritime targets. Despite the almost annual shortages of the funds needed to combat the underwater threat, no one in any position of authority questions the legitimacy of that threat. In fact, there are hundreds of possible underwater “disaster” scenarios that have been discussed by academics and publicized by the media, several imaginative novels have been written on the subject, and even a few movies have been produced focusing on the spectacular scenic and special-effects possibilities. Both Military and Civilian Targets One of the favorite scenario topics involves an attack – at sea or, preferably (from the terrorists’ point of view), in port – on cruise ships. Following is a typical setting:  A cruise ship sitting peacefully in an Italian harbor presents a glamorous picture of bright lights and happy passengers enjoying the evening’s entertainment. However, the ship also represents an important economic asset and is therefore an extremely tempting target for terrorists. A successful attack on the ship not only could cause a huge loss of life but also have a significant impact on the multi-billion dollar cruise-ship industry. Such fictional scenarios notwithstanding, the “diver threat” represents a real and present danger to the United States, which is by far the biggest and wealthiest trading nation in world history. Moreover, it is not only cruise ships that are threatened. John Mintz of the Washington Post reported – in a 31 December 2002 article (U.S. Fears Terrorists at Sea: Tracking Ships Is Difficult) – that Omar Al-Faruq, who wasentified in the media as a key Al-Qaeda operative, said after his arrest that he had planned to use divers to attack U.S. warships in Surabaya, Indonesia. A number of U.S. Coast Guard and U.S. Navy offices and agencies, especially the Naval Submarine Research Laboratory and the Coast Guard Research and Development Center (both of which are headquartered in Groton, Connecticut),  have been collaborating to address the potential threat posed by One of the favorite scenario topics involves an attack – at sea or, preferably (from the terrorists’ point of view), in port – on cruise ships. terrorist divers. To meet and defeat that threat they have developed what is generically called an anti-swimmer system, which typically consists of three major components–detection, warning, and deterrence. The system is operated by specially trained personnel, who work the system components, while Navy and Coast Guard divers handle system setup and other underwater tasks. Current and Continuing Collaboration The system’s principal detection component is an advanced sonar system that, coupled with special processing subsystems designed to detect approaching divers, is able to distinguish the humans from the fish and other marine mammals detected by the sonar. The warning component of the system, which is called an underwater loudhailer, was developed under a Coast Guard contract and tested by the Navy, and is specially designed to overcome the limitations caused by underwater speech distortion – and therefore can reliably communicate with divers. The loudhailer gives the swimmer defense team the ability to assess the diver’s intent – and then to react in a timely fashion if the diver does not respond to any warning that might be issued. This component of the system is intended to ensure there is enough time to dispatch a response boat to investigate the contact in greater detail and at closer range. This is done by approaching the contact very carefully and using imaging sonar to “see” the contact. After verifying that the contact is, in fact, a diver who is not responding to the warning that has been issued, the deterrence component of the system comes into play. The specific tactics are ified, but it is known that at least one deterrence component currently used compels the diver to surface. There are two key advantages of using this component. The first is that the intensity of the impulse transmitted to the diver can be scaled up or down to permit a range of non-lethal responses. The second is that the overall system itself is compact enough to be carried on a relatively small law-enforcement response boat.   The multi-layer approach described above is considered by defense officials to be a major step forward in addressing the critical issues facing U.S. swimmer defense teams operating in harbor environments. It allows detection of the threat, a determination of intent, and a method of responding to the threat in a non-lethal manner. In the long term, of course, those capabilities still might not be enough to detect, deter, and/or defend against a large-scale underwater attack against a major U.S. seaport. Which is why the current collaboration between the Coast Guard and the Navy undoubtedly will continue for the foreseeable future – and, assuming that the additional funding needed is provided by Congress, probably expand in both scope and capabilities.