I've written about drug smuggling semi-submersibles before. This story over at the Seattle Times is a pretty good one covering it from the angle of the US Coast Guard boarding team. From the piece:
The Coast Guard officer given the job of being in charge of boarding the narco sub was Lt. j.g. Lauren Milici, 24. She was packing a SIG .40-caliber service pistol, and her adrenaline was pumping.
Milici and her crew climbed into a smaller, 38-foot boat, and they soon were pulling up alongside the sub. In Spanish and English, they used a megaphone to order whoever was inside to come out. Receiving no response, they banged on the hull of the sub.
"It's always potentially dangerous. Essentially, you're the individual who's standing in somebody's way of picking up a paycheck for a successful delivery," said Milici, one of 20 women on the cutter.
Given the huge profits in smuggling illegal drugs, it's not exactly surprising the lengths that smugglers will go to to in getting their product from the coca fields to their customers. I always find these stories on drug smuggling subs interesting.
Of course if you can smuggle drugs to the US in one of these boats just imagine what else could be smuggled in. I am sure that you could fit a terrorist or two and some really nasty weapons in one of those. I guess the good thing for us is that the profit motive is terrorism is not quite as lucrative as narcotics.