They really do have everything in the Guinness Book of World Records:

A Korean submarine operator has broken the record for the longest accident-free operation and made the Guinness Book of Records. The record was broken by Kim Won-jang (48), a director of Seoguipo Submarine, a private tourist submarine operator in Jeju, and Kim Kwang-hyun (44), a division chief of the firm. On Monday they received official certification from the London-based Guinness World 18 years, nine months and 26 days of accident-free operations for from Dec. 22, 1988 until Oct. 17, 2007. Already in March they had received a certificate from the Korea Record Institute for 20,000 hours of accident-free operations of a tourist submarine.  [Chosun Ilbo]

I didn’t even know there was a tourism submarine on Cheju.  I’ll have to check it out the next time on Cheju.