Defense against swimmer incursions

Defenses against swimmer incursions are security methods developed to protect watercraft, ports and installations, and other sensitive resources in or near vulnerable waterways from potential threats or intrusions by swimmers or scuba divers. == Risks and threats == The need for military underwater security was demonstrated in World War II by the achievements of frogmen against armed forces facilities such as the 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.

Source: Wikipedia — Defense against swimmer incursions (CC BY-SA 4.0)