Finnish submarine Vetehinen Vetehinen was a Finnish 500 tonne Vetehinen class submarine that was constructed in the early 1930s , which served in the Finnish Navy during the second World War . The submarine was the first ship of its class of three submarines . The name " vetehinen " means " merman " . Combat operations . Winter War . The Finnish Navy was informed that Soviet 8 800 ton icebreaker " Yermak " would be arriving in the Baltic Sea from the Atlantic . " Vetehinen " was sortied to intercept the icebreaker off the port of Liepāja on the 4th of December . However , the submarine ran aground before reaching open sea and had to be pulled loose by tugs before it was able to start its voyage . " Vetehinen " arrived at the site on the 6th of December and started patrolling off the buoy on the port entrance . On the 7th of December it sighted the " Yermak " but was unable to reach it . While on station , " Vetehinen " encountered a couple of unknown submarines which were suspected to be of German origin . On the 8th of December " Vetehinen " began the voyage home and was attacked by Soviet submarine Щ - 324 ( Shch - 324 ) , but the attack failed and the Finnish submarine crew did not even notice the attempt . On the 12th of December " Vetehinen " was sortied again to intercept " Yermak , " this time on its voyage from Liepāja to Tallinn . However once again before reaching the open sea " Vetehinen " ran aground and had to be inspected before continuing on its mission the same day . Upon reaching the area the submarine was unable to sight the icebreaker and was recalled on the 14th of December . Continuation War . On 22 June 1941 " Vetehinen " laid 20 mines north of Kunda , and a further 17 mines on 28 June between Gogland and Bolshoy Tyuters . On 3 July 1941 " Vetehinen " encountered a freighter west of Gogland but due to distance was only able to damage it with its 76mm gun . On 3 August 1941 " Vetehinen " sighted a Soviet convoy consisting of pair of large minesweepers and a group of patrol boats escorting a group of Soviet submarines . One torpedo was launched at a distance of 1500 meters but without any effect . On 8 August 1941 " Vetehinen " launched two torpedoes at a 1500 ton freighter , but neither of the torpedoes exploded . The Italian torpedoes ( T / 40 Finnish designation ) proved to be unreliable in service despite functioning during test range firings . However it was later discovered that these torpedoes were unreliable when fired from a submerged sub because the increased water pressure caused the seals of the torpedo detonators to fail . For this reason a report that the Finns received from the besieged Hanko that a Soviet freighter had arrived there with two Finnish torpedoes still sticking from its hull became more believable . On 30 November " Vetehinen " sortied to intercept a convoy but was unable to reach it . On 3 December 1941 " Vetehinen " sighted a Soviet convoy headed due east from Hanko and engaged it . The submarine attacked on the surface but the poor quality of the night sight and the activity of the escort prevented torpedoes from being fired with any accuracy . " Vetehinen " fired both bow tubes and after turning around both aft tubes at the convoy without any effect , at an estimated distance of 2500 meters . A mere 15 minutes later the submarine sighted another Soviet convoy , this time headed due West , but had no loaded tubes and was unable to engage it . During 1942 " Vetehinen " was upgraded with new 12 - hydrophone listening arrays and equipped with a depth charge rack capable of carrying four depth charges . The submarine was further modified by streamlining the tower and moving the 20mm gun up to the tower . On 5 November 1942 , " Vetehinen " rammed the Soviet submarine " Щ 305 " ( " ShCh 305 " ) in the Sea of Åland and sank it . According to crew members still alive today , " Vetehinen " was on a night patrol searching for Soviet submarines , which stayed underwater during daytime but usually came up during the night to recharge their batteries . A contact was found , and after confirmation of an enemy contact " Vetehinen " launched a torpedo , which missed probably due to being fired at too short distance . " Vetehinen " opened fire with its deck guns . A second torpedo also missed , but the deck guns managed to damage the Soviet submarine which by then had started an emergency dive . The Captain of " Vetehinen " , determined not to let the submarine escape , ordered his submarine to ram the other vessel which at last was a success – the " teeth " on the bow of the ship ripped open the soviet submarine ' s hull and caused it to sink . " Vetehinen " suffered a minor leak because of the impact but managed to return to its home port . On 5 July 1944 " Vetehinen " laid 17 mines near Beryozovye Islands .