Sang-O-class submarine

The Sang-O class submarines are in use by North Korea, and are the country's largest home-built submarines. A single unit was captured by the Republic of Korea Navy (South Korea) after it ran aground on 18 September 1996 in the 1996 Gangneung submarine infiltration incident.

Sang-O II / K-300
It was widely reported in March 2011 that a new version of the Sang-O class had been deployed in North Korea. Satellite imagery from 2005 suggests the Sang-O II / K-300 may have been produced at the Mayang-do naval base and fitted out at the dry docks located at 39.9978 N, and 128.20019 E. Other footage of the nearby docks of Sinp'o appear to depict the Sang-O II / K-300 as early as 2004 (at 40 01'31.20"N 128 09'55.80"E). Subsequent satellite imagery shows the Sang-O II / K-300 deployed to the Ch’aho-rodongjagu submarine Navy Base at 40.205441 N 128.649524 E on North Korea's east coast.

According to the KPA Journal, the decision to develop a larger, improved version of the Sang-O came in the late 1990s or early 2000. The Sang-O II / K-300 is a stretched version of the original Sang-O class with an approximate length of 39 to 40 metres and a corresponding surface displacement of approximately 300 to 340 tons. The increased length and internal volume would suggest an increased in the operational range of the submarine and troop/equipment carrying capabilities. Top speed is also reported to be higher in the new model meaning an improved propulsion system is likely using some of the extra length.