The navies of both Koreas are capable of conducting effective underwater operations. The North Korean navy possesses more than seventy submarines that, while aging and relatively obsolete, remain difficult to detect. They are tasked mainly with disrupting South Korean sea lines of communication.
"Expanding the ROKN's Capabilities to Deal with the SLBM Threat from North Korea,"
Naval War College Review: Vol. 70
, Article 4.
Available at: http://digital-commons.usnwc.edu/nwc-review/vol70/iss2/4