Last year, 13 of the vessels were seized on dry land or stopped at sea by Colombian or U.S. patrol boats -- more than in the previous 14 years combined, according to the Pacific fleet of the Colombian navy, which is responsible for interdiction efforts across 130,000 square miles.

Naval officials say they are concerned that many more submarines may have gotten past patrols, especially now that the newest models are faster and feature more seaworthy designs than the first such vessels that Colombian officials discovered in 1993.

"This enemy is supremely intelligent and has lots of money," explained Adm. Edgar Cely, the navy's chief of operations. "It shows that the narco-traffickers are betting on this method."

This sparsely inhabited sliver of Pacific coastline, where muddy rivers loop into the ocean, has long been a smugglers' paradise. Behind the jagged cliffs that jut into the ocean is a vast jungle, laced with mangrove-fringed coves and virtually thousands of miles of waterways.

The topography is near ideal for transporting the cocaine produced in clandestine laboratories in nearby Nariño state, where leftist guerrillas, the remnants of a paramilitary army and drug traffickers try to outmuscle one another for control.

In recent years, traffickers have used speedboats, called "go-fasts," that are custom-made from fiberglass and mounted with powerful motors that can take them to nearly 60 mph. But the speedboats create long wakes, easy to spot from the air.

The new vessels are tougher to pin down. While popularly called submarines, they are, strictly speaking, submersibles. They cannot dive like true submarines. Still, the hull of such a boat glides beneath the waves, with only the cockpit and exhaust tubes visible from above.

Some of the new vessels, with whimsically shaped fins, and ducts and pipes sticking out, bring to mind Captain Nemo's Nautilus from Jules Verne's imagination. Others are cigar-shaped, narrow and hydrodynamic, not unlike the World War I German U-boats that prowled the North Atlantic.

Built under the jungle canopy, in camps outfitted with sleeping quarters for workers, the Colombian versions can cost $2 million and take nearly a year to build, said Capt. Gustavo Angel, commander of the 18-vessel flotilla that operates out of the naval base here in Bahia Malaga, Colombia's most important on the Pacific.

"What's most striking is the logistical capacity of these criminals to take all this material into the heart of the jungle, including heavy equipment like propulsion gear and generators," said Angel, who has spent years fighting drug traffickers.

For traffickers, the payoff -- reaching Central America, the first stage in a circuitous route to the United States -- is well worth the trouble. A 10-ton load can fetch nearly $200 million wholesale in the United States.

One of the vessels on display here, resting on wooden blocks on the naval dock after being seized shortly after its construction, has a 450-horsepower diesel engine that could power the craft to North America. At 60 feet in length, it is designed to reach speeds of 11 1/2 mph and carry up to 10 tons of cocaine, five times as much as a "go-fast."

Because it was sheathed in fiberglass -- indeed, much of its superstructure is fiberglass -- it is virtually impossible to detect via sonar. It also has ballast tanks for balance and a global positioning system for navigation. Officials here have grudging admiration for the engineers who designed the vessels, saying they were built to cut through water seamlessly while withstanding long voyages.

"If you look at this, they respect the norms of naval construction," said Lt. Manuel Higuera, moments after lowering himself through the hatch. "It's reinforced so the submersible can have a great resistance."

Still, the submersible -- one of three on display here in Bahia Malaga -- is no Red October.
There's no bathroom, no private sleeping quarters -- let alone a galley or torpedo room. For the pilot and three crewmen, operating space was cramped. The craft has a ventilation system, but with the engine rumbling just two feet away, the heat was likely unbearable, officials here theorize.

The idea, officials here say, was to beach the vessel, unload the cocaine and leave it behind.
"The question that is up in the air is how many have gotten out," said Angel.
Some have surely made it far. In 2006, a 33-foot sub was found abandoned on the northern coast of Spain, where the authorities suspect the crew had unloaded a cargo of cocaine before fleeing.

In 2000, Colombian police discovered a 78-foot submarine, half-built with the help of Russian engineers, in a warehouse outside Bogota high in the Andes.

The authorities said the plan had been to complete construction and transport the parts to the coast, where the sub would have been reassembled. The double-hulled vessel could have traveled 2,000 nautical miles, dived 330 feet and carried 150 tons of cocaine.

Little is known about who is behind the new submersibles.
But the navy says there is evidence that the Revolutionary Armed Forces of Colombia, a rebel army, is collaborating with trafficking groups to find ways to transport cocaine, including commissioning construction of submersibles. Authorities said they cannot discount the possibility that former naval officers might be working for traffickers, helping design the vessels.

"The people who know about submarines are military men," said a high-ranking naval officer who has investigated the submersibles.

Arrests are rare. When clandestine shipyards have been discovered, the workmen have scampered into the jungle. When the vessels have been stopped at sea, the crews have scuttled them, sending boat and cocaine to the bottom.

"The last one out opens up the valves and we cannot enter until the crew comes out, since there's only one space to get in and out," said Cely, the admiral.

With no evidence of trafficking against them, the crewmen go from suspected traffickers to castaways who, in accordance with maritime law, must be rescued.

Here in the navy yard, in addition to the seized submersibles, there is a torpedo-like tube, designed to carry cocaine, that traffickers planned to attach by cable to a ship. There are also several "go-fasts" and an earlier mode of transport for drugs -- fishing trawlers -- now rotting in dry dock. Together, they could make up a Smithsonian exhibit.

Some officials say the submersibles should be destroyed.
"We've been debating what to do with them," Angel said. "I'm partial to keeping them because they are part of the history of our country. And when we put an end to drug trafficking, our sons and grandsons should know what these criminals did."