Finnish submarine Vesihiisi


Vesihiisi was a Finnish 500-tonne that was constructed in the early 1930s. The vessel served in the Finnish Navy during the second World War.

German design ''Iku-Turso'', ''Vesihiisi'', ''Vetehinen''

While preparing the design of the, the Germans also prepared a design for a seagoing submarine for the Finnish Navy. Three submarines were built to this design, and like Saukko, they were fitted for mine-laying, the mines being supplied by the Germans. Being designed for use against Soviet bases, radius of action was not of prime importance to this design, and only 20 tons of fuel oil were carried (as opposed to the 67 tons carried by the German Type VIIa based on this design.

Combat operations

Winter War

Vesihiisi was alerted with Vesikko to Hanko region on 30 November 1939 as several Soviet surface combatants were headed towards the area. The submarines however failed to arrive to the area in time to intercept the and its escorts.
Vesihiisi ran aground in early December 1941 and had to be docked for a few days for repairs. On 27 December Vesihiisi laid 16 mines off the Soviet naval station of Paldiski but soon after the ice forced the submarine to stay in port.

Continuation War

Vesihiisi started the Continuation War on 22 June by laying 20 mines in Estonian waters. She laid 18 more mines on 24 June at Ruuskeri south southwest from Gogland and further 18 mines on 26 June southeast from Bolshoy Tyuters. After this the mining operation was postponed and Vesihiisi laid the 18 already loaded mines finally on 2 August east of Osmussaar.
On 2 July 1941 Vesihiisi while patrolling east of Gogland encountered an escorted freighter heading east. A torpedo attack failed and the submarine suffered light damage from the escort's depth charges.
On 5 August 1941 Vesihiisi attacked a convoy transporting supplies to besieged Soviet garrison at Hanko. The convoy consisted of a transport vessel of Molotov class escorted by pair of large minesweepers and group of patrol boats. The submarine penetrated the escort screen and launched two torpedoes at a range of while being between the target and the escorts. Neither of the torpedoes exploded and the escorts forced Vesihiisi to dive to the depth of. Though the submarine did not suffer severe damage from the depth charges the repairs on the dock lasted for a week.
In December 1941 after the Soviets had evacuated Hanko the Finnish submarines were docked for the winter. During the sailing season of 1941 the Italian torpedoes Vesihiisi used proved to be unreliable. During 1942 Vesihiisi was upgraded with new 12-hydrophone listening arrays and equipped with depth charge rack capable of carrying 4 depth charges. The submarine was further modified by streamlining the tower and moving the 20 mm gun up to the tower.
On 9 August 1942, Vesihiisi was deployed along with her two sister ships to Mariehamn. Their mission was to conduct anti-submarine and escort operations in the Sea of Åland. In the evening of 21 October 1942 she torpedoed and sank the Soviet S-class submarine, near Lågskär in the Sea of Åland. The captain and three of the crew of S-7; all of whom had been in the submarine's tower, were then captured.
On 4 July 1944 Vesihiisi laid 20 mines between Moshchny Island and Seskar. The boat was attacked with depth charges by two Soviet minesweepers but was able to escape without any damage. The submarine laid further 18 mines north of Moshchny Island on 6 July 1944.