a means for detecting and destroying submerged submarines.
There are signaling and positional antisubmarine nets. A signaling net emits a signal indicating the presence of a submarine inside the net. A positional net consists of a metal base held in place by anchors and of steel-mesh panels fastened to the base. The upper edges of the panels (the head ropes) have glass balls in hemp braiding attached to them to keep the net afloat. Special cartridges with explosive charges are suspended on cables from the panels. If a submarine hits the net, a panel is torn from the base and an explosion occurs, which destroys the hull of the submarine. Instead of explosive cartridges, signaling nets use signal buoys, which are filled with a smoke-producing mixture or with a substance to color the water. If a submarine hits the net, a buoy rises to the surface of the water and thus indicates the location of the submarine. Antisubmarine nets are laid by ships called netlayers.