In South Korea has a problem with wealthy North Koreans escaping to South Korea via small boats. Several of these boats have recently made their way from the north to the south, and entered South Korean ports without ever being spotted by coastal radars, or coast guard ships or aircraft. These small boats are hard to spot way offshore, as the coastal radars are not able to detect small boats that are so low in the water. This has made public something the military would rather be kept secret, that North Korean commandos have long sneaked in via small, fast boats.
The new phenomenon is all about money. As some North Koreans become wealthier via the markets the government has legalized in order to alleviate the widespread hunger (and growing discontent), they can afford to buy small (7 meter or so) boats, and equip them with outboard motors (that can take them hundreds of kilometers out to sea) and escape capture by the coast guard (which intensely patrols coastal border areas up to about 20 kilometers out.)
In reaction to the situation, earlier this year the South Korean Coast Guard bought four CN-235-100 transports from Indonesia. The CN-235s were jointly developed by Spain and Indonesia. These two engine transports will be converted to maritime patrol aircraft, and will cost about $23 million each. The 16 ton CN-235 can carry four tons of equipment and stay in the air for about eight hours per sortie. Cruse speed is about 380 kilometers an hour. The search radar can see out to 360 kilometers, and track up to a hundred ships (including very small ones) at once. Adding radio and communications equipment for maritime patrol work adds about $10 million to the cost of each CN-235.
Currently the South Korean coast guard has fifteen helicopters and one patrol aircraft, so the four CN-235s will be a big boost to coastal patrol capabilities. South Korea has 2,400 kilometers of coastline to watch. But only about twenty percent of that, where Chinese and North Korean fishing boats often work illegally, need to be watched carefully.