Torpedo net Torpedo nets were a passive naval warship defensive device against torpedo es . Their use was common practice from the 1890s through World War II . Torpedo nets were superseded by the anti - torpedo bulge and torpedo belt s . Origins . With the introduction of the Whitehead torpedo in 1873 , and the subsequent development of the torpedo boat , new means were sought to protect capital ship s against these underwater attacks . In 1876 the British Admiralty Torpedo Committee came up with a number of recommendations for combating torpedoes , which included " . . . nets of galvanised iron hung around each battleship from projecting 40ft spars " . Experiments were conducted in 1877 , with HMS " Thunderer " becoming the first operational ship to be fitted with the nets . Early nets were referred to as the " Bullivant type " after the London - based company that produced them . They were constructed from steel hoops linked by smaller hoops to form a mesh , with an approximate weight of one pound per square foot ( 5 kg / m² ) . These nets were projected out from the sides of the ship on wooden poles . Extensive tests were conducted , with the nets proving capable of stopping the contemporary torpedo without being damaged . A torpedo with a warhead proved capable of causing limited damage to the net . A heavier net was introduced in 1894 consisting of hoops with a weight of five pounds per square foot ( 25 kg / m² ) . Torpedo net cutter . The adoption of these nets resulted in the introduction of the torpedo net cutter on the nose of torpedoes , either in the form of scissors in Japanese designs , or a French pistol - powered version . Later heavier , denser nets used by the German and British navies were regarded as " torpedo - proof " . Design and use . In addition to new tactical measures ( e . g . , greater harbor security and rotation of moored vessels out to sea ) , beginning in 1904 major navies sought a device for protection against torpedo boat attack . Torpedo nets were the favoured solution . These were heavy steel mesh nets that could be hung out from the defending ship , when moored or otherwise stationary in the water , on multiple horizontal steel booms . Each boom was fixed to the ship at one end at or below the edge of the main deck , by a steel pin that permitted the boom to be swung against the ship and secured when the ship sailed . A series of such booms were so fixed at intervals along each side of the ship . When the ship was moored , the free ends of the booms could be swung out with the net hung on the outer ends , thus suspending the net at a distance from the ship equal to the length of the boom , all around the ship . With the net mounted , a torpedo aimed at the ship would hit the mesh net and explode at a sufficient distance from the hull to prevent serious damage to the ship . Russo - Japanese War 1904 - 1905 . In spite of fitting the major ships with anti - torpedo nets , and close danger of war , the Russians did not deploy the nets during the Japanese destroyer torpedo attack on the Imperial Russian Navy stationed on a roadside of Port Arthur on 8 February 1904 , which was the opening shots of the Russo - Japanese War . During other actions later in the war nets were used effectively by the battleship " Sevastopol " . At the end of the siege of Port Arthur , that vessel was anchored outside the harbor in a position where she was sheltered from the fire of the Japanese batteries but became exposed to persistent attacks from torpedo boats . From 11 to 16 December 1904 , " Sevastopol " was exposed to numerous night attacks . The Japanese employed no fewer than 30 torpedo - boats , of which two were lost , and it was estimated that altogether 104 torpedoes were fired against the ship . One torpedo exploded in the nets near the bow and produced a leak in the torpedo room ; another damaged the compartment forward of the collision bulkhead , because the nets yielded to such an extent that the explosion took place near the hull . The last two torpedoes that struck the ship were fired at close range against the unprotected stern : they damaged the rudder and produced a serious leak under the quarterdeck , so that the aft end of the ship sank until it touched the bottom . The leak was repaired . The ship again floated and on the last day of the siege she was taken out to deep water and sunk . Decline . The sinking by torpedo of three Allied battleships during the 1915 Dardanelles Campaign , all with torpedo nets deployed , demonstrated that the increased speed of newer torpedoes and the tactic of firing several torpedoes at the same location on the target had made the torpedo net ineffective . Torpedo nets were superseded by the anti - torpedo bulge and torpedo belt s . However , torpedo nets continued in use during World War II to protect ships at anchor , especially as obstacles against submarines , human torpedo es , and frogmen . They were also used to protect dams , and led to the development of bouncing bomb s to defeat them , as in Operation Chastise .