DEA agents prowl Colombia's international airport, tracking drug couriers and seeking to bust a smuggling ring operated by U.S. military personnel.

DEA agents target an elusive cartel in the Caribbean, pursuing the notorious "go-fast" speedboats that transport millions of dollars of illicit cargo.

The agents search the waters of Cartagena for submarines that can hold seven tons of coke. Once caught easily, the subs have become hard to locate.

Traffickers often force desperate people to transport their products, and it's up to the DEA to stop the couriers, even at risk to their own lives.