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

Related documents: [0]  [DOC] 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. [END] 
[1]  [DOC] 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. [END]  
Answer: 1981
1981