Semi-submersibles are custom-built of wood, fiberglass and other materials that have low radar reflectivity, making them very difficult to detect electronically. (U.S. DOD)

There have been some spectacular examples lately of the consequences of trying to smuggle drugs into the United States by sea, with at least four “go-fast” boats and their crews ending up as burning wrecks in the Caribbean after U.S. missile strikes.

Whether you agree with this frontier-style justice or not, there’s no question it must be giving those who operate the boats serious doubts about their career choice.

The sleek, high-speed “go-fast” boats—often locally built versions of offshore racing hulls up to 40 feet long and powered by multiple big outboards—are only part of the shadow fleets that, by some estimates, move more than 2,000 tons of cocaine, fentanyl, and other drugs toward U.S. shores each year. The result is tens of thousands of American deaths annually, along with the social and economic wreckage that follows widespread addiction.

Part Boat, Part Submarine

While powerful radar and real-time satellite surveillance make it relatively easy for U.S. forces to spot these surface-speed operations, the bigger challenge now lies below the waves. Increasingly, the contraband moves aboard semi-submersibles, also known as “narco-subs.”

These hybrid craft are engineered to move large loads while keeping a low profile—literally. They typically measure between 30 and 70 feet in length, constructed from fiberglass, wood, or composite laminates with ballast tanks and a waterline so low that only a small canopy or snorkel breaks the surface. Propulsion is almost always diesel, trading speed for endurance. Most travel at 6 to 12 knots but can cover hundreds or even thousands of nautical miles, carrying multiple tons of narcotics in a single trip.

The earliest versions of these craft began appearing in the late 1990s off Colombia and Ecuador. By the mid-2000s, semi-submersibles had evolved into a mainstay of the drug trade, with many captured each year by the U.S. Coast Guard and the Colombian Navy. Dozens have been seized since 2019 alone, including several sophisticated models with GPS navigation, multiple engines, and stealth coatings to reduce heat and radar signature.

Interdiction of semi-submersibles is difficult but not impossible—numerous vessels are captured every year. (U.S. DOD)

Unmanned Vessels: Drones of the Sea

Not surprisingly, a few unmanned semi-submersibles have now been captured—an innovation that likely represents the future of maritime smuggling. These craft are remotely operated via satellite link, eliminating the need for air supply, bunks, or toilets. Without human crew, they can be smaller, stealthier, and harder to detect.

In mid-2025, the Colombian Navy intercepted what appeared to be a fully remote-controlled narco-sub in the Caribbean, complete with antennas, cameras, and a Starlink satellite terminal. It carried no drugs but was believed to be a test platform for cartel engineers. European law enforcement has reported similar discoveries.

There are also credible reports of fully submersible vessels—true submarines—being built in remote jungle workshops. Some of these are capable of traveling hundreds of feet below the surface, beyond the reach of conventional radar or infrared surveillance.

Most semi-submersible captures thus far have been well away from U.S. shores but some of the vessels have the capability to travel well into U.S. waters. (U.S. DOD)

Danger on the High Seas

For mariners, the takeaway is simple: these are criminal operations, and engagement is strictly for law enforcement. Recreational boaters who venture offshore should avoid approaching any low-profile, unattended vessel and immediately report sightings to the U.S. Coast Guard. Accurate position, heading, and description can make the difference in an interception.

High-speed pursuits and interdictions can be extremely dangerous. Boats may be scuttled or set afire to destroy evidence, and traffickers have been known to carry weapons. Even professional boarding teams must balance aggression with safety and legal constraints.

The broader challenge remains daunting. So long as the major producing nations fail to crack down on the source, and as long as U.S. cities struggle with demand and enforcement, even the might of the U.S. Navy and Coast Guard will find it difficult to stop every shipment.

Still, every seizure and every destroyed narco-sub represents a small victory in a shadow war that continues just beyond the horizon—one where speed, stealth, and vigilance determine who controls the Caribbean’s dark lanes.

— Frank Sargeant 
frankmako1@gmail.com