Here is a scenario idea based on a real-world situation.
Water mass mistaken for submarine sparks fears of N. Korean infiltration
By Kim Deok-hyun
SEOUL, Sept. 8 (Yonhap) — A large water mass mistaken for a midget submarine triggered a false alert of a possible North Korean infiltration early Wednesday, prompting a South Korean Navy patrol ship to drop anti-submarine bombs on the underwater object, military officials said.
Troops and coast guard officials had been on alert for several hours earlier in the day after a Lynx helicopter, while on a routine training mission, detected the underwater object in waters 15 kilometers off the eastern coastal city of Donghae.
In this scenario we can have a ROKN Lynx helo and at least one patrol ship (FFL or PCC-class?) prosecuting a nKN midget submarine. The midget submarine may be armed (like the March 2010 Choenan attack) or could just be trying to get by to infiltrate secret agents (like the 1998 midget submarine caught in fishing nets).
