Anti-frogman techniques

Anti-frogman techniques are security methods developed to protect watercraft, ports and installations, and other sensitive resources both in or nearby vulnerable waterways from potential threats or intrusions by frogmen or other divers.

In World War II this need for military underwater security was first shown by the achievements of frogmen against armed forces facilities: see for example Italian frogman actions in WWII. Since the late 1950s, the increasing demand for and availability of sophisticated scuba diving equipment has also created concerns about protecting valuable underwater archaeology sites and shellfish fishing stocks.

The 12 October 2000 USS Cole bombing was not carried out by underwater divers, but did bring renewed attention to the vulnerability they present for naval ships. Divers can swim 100 to 200 yards in three minutes time, and large sonar ranges would need to be established around ships in order for security forces to detect underwater swimmers in time to make a sufficient response.

In March 2005 the Philippine military, interrogating a captured anti-government terrorist bomber, found that two of Southeast Asia’s most dangerous terrorist organizations linked to Al Qaeda were said to be jointly training militants in scuba diving for attacks at sea.

Hereinafter, "nlsn" = "Non-Lethal Swimmer Neutralization Study"

Following World War II, the increasing popularity in recreational diving introduced a new complexity to underwater security. Divers must not only be detected, but evaluated as to their purpose or intentions for swimming in monitored areas. Steps to protect against threat or harm from divers must take into account possible reasons why they would be swimming in monitored areas. The divers may be:

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