This article is one of many about current tensions in the Koreas. I'd suggest reading https://www.reddit.com/r/NorthKoreaNews or https://twitter.com/BuckTurgidson79 for a broader overview of the situation. I bring this up on a tech site because of the potential issues these tensions could create.
Good luck finding those diesel-electric boats.
If they manage to creep away from the AOE, they could be anywhere.