North Korea Submarine : real threat for South Korea NAvy

The latest news says that North Korea has accused South Korean who is responsible for the sinking of the ship corvette Cheonan around April 2010.
If the allegations are true, then the presumption that North Korean conventional capabilities far below the south korea is a big mistake.
North Korean capabilities of military operations under the sea without being able to be detected by the ship south korea north korea able to show that given the balance of military power at sea.
As is known, that during this capability north korea navy with the ability to be adrift far south korea navy. Owned submarine north korea generally come from china, and some of the domestic production (class submarines Sang-O).
Then the question is whether the North Koreans with operating profits sink ships south korea?

North Korea clearly shows that they have the combat capability commensurate with the sea south korea. Especially in the last fire exchange, north korea always suffered greater losses than south korea. This can also be intended as propaganda for the people of north korea country's military capability.