Sang-O-class submarine

The Sang-O ("Shark") class submarines are diesel-electric coastal submarines operated by the Korean People's Navy of North Korea, serving as the country's second-largest indigenously built submarines. As of February 2021, North Korea maintains approximately 40 Sang-O-class submarines.

Introduced in 1991, these submarines were produced at the Bong Dao Bo Shipyards in Sinpo. In 1996, a Sang-O-class submarine was captured by the Republic of Korea Navy after running aground during the Gangneung submarine infiltration incident. This captured vessel is now on display at Unification Park near Gangneung, which opened in 2001.

The Sang-O class is larger than midget submarines but smaller than Romeo and Whiskey-class submarines. They are typically equipped with four 533 mm torpedo tubes and can carry up to 16 mines. Some variants are unarmed and instead serve as platforms for transporting North Korean commandos.

In March 2011, a new version of the Sang-O class, known as the Sang-O II or K-300, was reportedly deployed. Satellite imagery suggests production began at the Mayang-do naval base around 2005, with initial sightings in Sinpo's docks as early as 2004. The Sang-O II features an extended length of approximately 39 to 40 meters and a surface displacement of 300 to 340 tons. This design improvement increases operational range, troop-carrying capacity, and top speed, indicating an enhanced propulsion system.

The decision to develop the improved version was made in the late 1990s or early 2000s, reflecting North Korea's efforts to modernize its submarine capabilities.