Dubbed "PLUTO," after the planet that is so difficult to spot, the semi-submersible craft serves as a realistic practice target for the detection systems of the department and its national security community partners, a DHS release reported Monday.
In a typical operation, PLUTO will operate at cruising speeds of 4 to 8 knots while remote sensor platforms from sea to space attempt to detect and track it at various distances and observation angles, the release said.
In 2006, following years of rumors that drug cartels were using such watercraft, a Colombian semi-submersible was captured by the U.S. Coast Guard in the eastern Pacific Ocean.
Drug cartels are still building and using vessels with low profiles and low radar reflectivity that cut through water at wave height and are nearly impossible to detect, officials said.
"Small surface vessels, self-propelled semi-submersibles, and now the most recent innovation of fully submerged vessels (FSVs), pose significant challenges to maritime security," Tom Tomaiko of the department's Science & Technology Directorate said.
"While some small boats sitting low in the water have legitimate purposes, there are many that are used for illicit purposes."
If the "narco" subs escape detection and the drugs are successfully delivered, the vessels are typically scuttled and not reused.
"Drug-running is lucrative. It is cheaper to simply build another vessel than to run the risk of trying to get a vessel and its crew home," Tomaiko said.