Question: In what year did the submarine that sank the Tsushima Maru open to public tours?

full_context: Document 1: Tsushima Maru: Tsushima Maru (対馬丸) was a Japanese passenger/cargo ship that was sunk by the submarine USS "Bowfin" during World War II, while carrying hundreds of schoolchildren from Okinawa to Kagoshima.
Document 2: Japanese minesweeper Tama Maru No. 2: The Tama Maru No. 2 was a 264 gross ton whaler built by Mitsubishi Jukogyo Kabushiki Kaisha, Kobe for Taiyo Hogei Kabushiki Kaisha in 1936. She was requisitioned in 1941 by the Imperial Japanese Navy during World War II and converted into a minesweeper. On 10 March 1942, during the invasion of Lae-Salamaua, "Tama Maru No. 2" was damaged by Douglas SBD Dauntless dive bombers from the United States Navy aircraft carriers USS "Lexington" and USS "Yorktown" off Lae, New Guinea.
Document 3: Ehime Maru and USS Greeneville collision: The "Ehime Maru" and USS "Greeneville" collision was a ship collision between the United States Navy (USN) "Los Angeles"-class submarine USS "Greeneville" (SSN-772) and the Japanese-fishery high-school training ship "Ehime Maru" (えひめ丸) from Ehime Prefecture on 9 February 2001, about 9 nmi off the south coast of Oahu, Hawaii, United States. In a demonstration for some VIP civilian visitors, "Greeneville" performed an emergency ballast-blow surfacing maneuver. As the submarine shot to the surface, she struck "Ehime Maru". Within 10 minutes of the collision, "Ehime Maru" sank. Nine of the people on board were killed: four high-school students, two teachers, and three crewmembers.
Document 4: Attack on Sydney Harbour: In late May and early June 1942, during World War II, submarines belonging to the Imperial Japanese Navy made a series of attacks on the cities of Sydney and Newcastle in New South Wales, Australia. On the night of 31 May – 1 June, three "Ko-hyoteki"-class midget submarines, each with a two-member crew, entered Sydney Harbour, avoided the partially constructed Sydney Harbour anti-submarine boom net, and attempted to sink Allied warships. Two of the midget submarines were detected and attacked before they could successfully engage any Allied vessels, and the crews scuttled their boats and killed themselves. These submarines were later recovered by the Allies. The third submarine attempted to torpedo the heavy cruiser USS "Chicago" , but instead sank the converted ferry HMAS "Kuttabul", killing 21 sailors. This midget submarine's fate was unknown until 2006, when amateur scuba divers discovered the wreck off Sydney's northern beaches.
Document 5: SS Brown Victory: The SS "Brown Victory" was a Victory-class cargo ship built during World War II under the Emergency Shipbuilding program. The SS Brown Victory (MCV-712), was a type VC2-S-AP2 victory ship built by Oregon Shipbuilding Company Portland. The Maritime Administration cargo ship was the 171th ship built. Its keel was laid on February 25, 1945. The ship was christened on May 2, 1945. The SS "Brown Victory" was an armed cargo ship, named for Brown University one of 150 educational institutions that had Victory ships named after them. She was commissioned February 23, 1945 at the Oregon Shipbuilding yards. The 10,600 ton ship was the 171th Victory type ship constructed for the Maritime Commission. She was operated by the Alaska Packers Company under the United States Merchant Marine act for the War Shipping Administration.
Document 6: Battle of Tsushima: The Battle of Tsushima (Russian: Цусимское сражение , "Tsusimskoye srazheniye"), also known as the Battle of Tsushima Strait and the Naval Battle of the Sea of Japan (Japanese: 日本海海戦, "Nihonkai-Kaisen") in Japan, was a major naval battle fought between Russia and Japan during the Russo-Japanese War. It was naval history's only decisive sea battle fought by modern steel battleship fleets, and the first naval battle in which wireless telegraphy (radio) played a critically important role. It has been characterized as the "dying echo of the old era – for the last time in the history of naval warfare, ships of the line of a beaten fleet surrendered on the high seas".
Document 7: USS Bowfin (SS-287): USS "Bowfin" (SS/AGSS-287), a "Balao"-class submarine, was a boat of the United States Navy named for the bowfin fish. Since 1981, she has been open to public tours at the USS "Bowfin" Submarine Museum and Park in Pearl Harbor, Hawaii, next to the USS Arizona Memorial Visitor Center.
Document 8: HA. 19 (Japanese Midget Submarine): The HA. 19 (also known as Japanese Midget Submarine "C" by the US Navy) is a historic Imperial Japanese Navy "Type A Kō-hyōteki"-class midget submarine that was part of the Japanese attack on Pearl Harbor on 7 December 1941. This submarine was ordered to enter Pearl Harbor then attack the American warships with its torpedoes and then be scuttled with explosives next to a warship. However, she did not enter the harbor, and was grounded and captured. The submarine was eventually put on display near the submarine squadron at Naval Station Key West, Florida, then moved to the nearby Key West Lighthouse and Military Museum. "HA. 19" is now displayed at the National Museum of the Pacific War in Fredericksburg, Texas.
Document 9: USS Razorback (SS-394): USS "Razorback" (SS-394), a "Balao"-class submarine , was the only ship of the United States Navy to be named after the razorback, a species of whale ("Balaenoptera physalus") found in the far southern reaches of the Pacific Ocean. It is arguably the longest-serving submarine still existing in the world, having been commissioned by two different countries for 57 years of active duty. In 2004, the state of Arkansas adopted the submarine (although it was not named after the University of Arkansas mascot) and is now a museum ship at the Arkansas Inland Maritime Museum.
Document 10: USS Arizona salvaged artifacts: Some of the USS "Arizona" salvaged artifacts, taken from the wreck of that battleship after it exploded and sank in the Attack on Pearl Harbor, are displayed in several locations in the U.S. State of Arizona. The term "marine salvage" refers to the process of recovering a ship, its cargo, or other property after a shipwreck. This is a list of those artifacts recovered from the shipwreck. These artifacts are on display in the Arizona State Capitol Museum, the Carl T. Hayden Veterans Administration Medical Center and in the Wesley Bolin Memorial Plaza, all of which are located in Phoenix. One of two salvaged bells of USS "Arizona" is on display in the University of Arizona Student Union Memorial Center in Tucson, and Glendale Veteran’s Memorial in the city of Glendale, Arizona is constructed using material from the wreck of the battleship.
Document 11: Tambor-class submarine: The "Tambor"-class submarine was a United States Navy submarine design, used primarily during World War II. It was the USN's first fully successful fleet submarine, and began the war close to the fighting. Six of the class were in Hawaiian waters or the Central Pacific on 7 December 1941, with "Tautog" at Pearl Harbor during the attack. They went on to see hard service; seven of the twelve boats in the class were sunk before the survivors were withdrawn from front-line service in early 1945; this was the highest percentage lost of any US submarine class. "Tautog" was credited with sinking 26 ships, the largest number of ships sunk by a US submarine in World War II. The "Tambor"s retained the top speed of 21 kn and range of 11000 nmi (allowing patrols in Japanese home waters) of the preceding "Sargo" class , and improvements included six bow torpedo tubes, a more reliable full diesel-electric propulsion plant, and improved combat efficiency with key personnel and equipment relocated to the conning tower. In some references, the "Tambor"s are called the "T Class", and SS-206 through SS-211 are sometimes called the ""Gar" class".
Document 12: Attack on Pearl Harbor in popular culture: The attack on Pearl Harbor has received substantial attention in popular culture in multiple media and cultural formats including film, architecture, memorial statues, non-fiction writing, historical writing, and historical fiction. Today, the USS "Arizona" Memorial on the island of Oahu honors the dead. Visitors to the memorial reach it via boats from the naval base at Pearl Harbor. The memorial was designed by Alfred Preis, and has a sagging center but strong and vigorous ends, expressing "initial defeat and ultimate victory". It commemorates all lives lost on December 7, 1941.
Document 13: New Jersey Naval Museum: The New Jersey Naval Museum (NJNM), located along the Hackensack River in Hackensack in Bergen County, New Jersey, United States, is dedicated to the state's Navy heritage and naval history in general. The prominent element in the collection is the USS "Ling" (SS-297), a 312 ft long "Balao"-class submarine of World War II. The museum is located along River Street and is operated by the Submarine Memorial Association.
Document 14: SS John W. Brown: SS "John W. Brown" is a Liberty ship, one of two still operational and one of three preserved as museum ships. As a Liberty ship, she operated as a merchant ship of the United States Merchant Marine during World War II and later was a vocational high school training ship in New York City for many years. Now preserved, she is a museum ship and cruise ship berthed at Clinton Street Pier 1 in Baltimore Harbor in Maryland.
Document 15: RMS Nova Scotia (1926): RMS "Nova Scotia" was a  GRT UK transatlantic ocean liner and Royal Mail Ship. In World War II she was requisitioned as a troop ship. In 1942 a German submarine sank her in the Indian Ocean with the loss of 858 of the 1,052 people aboard.
ground_truth: 1981