Narco-subs and the Colombian drug trade: the ultimate "white whale"

They're called "narco-subs," and over the last two decades, they've carried billions of dollars' worth of cocaine to Mexico, which has ended up on the streets of the U.S. and Canada.

But last week's capture of another narco-sub -- this one carrying more than five thousand kilograms of cocaine -- may help herald the end of the practice, says Javier Guerrero, a Colombian sociologist PhD student who specializes in drug-smuggling techniques.

The U.S. Coast Guard released video of the capture, below.

But for every submarine that gets caught, at least two are getting through, Guerrero tells Day 6 host Brent Bambury. And the four crew members who sail the craft take enormous risks sailing what the drug cartels call "cold-water-coffins."

"It's pretty claustrophobic. You have four people in there eating canned food for five days. It's pretty hard conditions," he says. But if they don't sink, get hit by another ship or get caught, they make about $10,000 for the trip, he adds. That's compared to the $200 they might make in a month at home. "The risk is really high, but the reward is pretty high, too."

The subs are simply constructed, he says. "The cocaine is usually stored at the front of the ship, and then you have small space for the crew, and then at the back of the ship is the engine." There are no proper bulkheads to keep sections airtight, he says. If they get a hole, "they just sink," he says.

About 80 subs have been captured, many in the open sea, but most near or on the shore, he adds. The technology has improved incrementally. Initially, for example, many were caught because authorities could see the heat signatures from their engines. So now the engines are covered with lead shielding to prevent this. "They learn by trying, they learn by doing, trial and error, basically."

There are now several fully submersible submarines in action, he believes.

However, Guerrero thinks the days of the narco-sub are numbered. "They know now that the Colombian Navy and law enforcement have improved in the detection of the narco-subs, so probably they will change. They won't invest in the narco-subs any more in the near future."