Strategy Page reports that the set of almost-complete submarines built by a drug cartel in Colombia were much more sophisticated and capable than first thought:
The leader (Mauner Mahecha) of the project was a guy in his early 30s with no boat building experience but excellent organizational and leadership skills.
Mahecha had a huge budget and used it to find and hire men with the needed skills or experience with submarines. Mahecha also quickly recruited additional specialists as needed and obtained whatever materials the builders called for. His project built three submarines, and the project was shut down because one of the men recruited (an experienced engine mechanic working for the Colombian Navy) managed to tip off the Colombian Navy intelligence and then the U.S. about the project.
The Mahecha submarines, when closely examined by experts, turned out to be more sophisticated than first thought. The outer hull was made out of strong, lightweight, Kevlar/carbon fiber that was sturdy enough to keep the sub intact but very difficult to detect with most sensors. The hull could not survive deep dives but this boat didn’t have to go deep to get the job done. The diesel-electric power supply (up to two-hundred and forty-nine lead-acid batteries), diving and surfacing system, and navigational systems of captured subs were all in working order. Those who built these boats apparently borrowed much from recreational subs. The sub builders also had impressive knowledge of the latest materials used to build exotic boats.
The three fiberglass/Kevlar submarines were obviously built to transport cocaine to North America and the existence of a building effort had been detected by intel agencies. For several years before the submarine boat yard was discovered the U.S. Navy, in cooperation with some Central and South American navies, have been looking for these subs, at sea and on land. While these submarines didn’t run very deep (less than twenty meters/sixty-two feet), they are invisible to most sensors when completely submerged. These subs were designed to run on batteries for up to eighteen hours, before having to surface and recharge. When they are at sea, they usually operate their diesel engines. These are noisy. Sonar can pick up this noise over a long distance. By capturing these subs it was possible to run the engines and get a sound profile of this type of boat and equip American sonar systems with this data. These subs had a range (on internal fuel) of about twelve-thousand kilometers. Thus, the boat could get from Colombia to southern California and back. These drug gangs spent over two million on each of these subs.
The most potent weapon the U.S. Navy has against these tiny (less than thirty-four meters/one-hundred foot long) subs is heat sensors, but even that may have had limited effectiveness. That’s because one of the subs captured had a snorkel type device (a tall structure extending from the conning tower, which contained pipes allowing diesel exhaust to escape and fresh air to be brought into the submerged boat.) It’s this heat that airborne sensors can detect. All surface (or semi-submerged) ships at sea display this kind of “heat signature”, and capturing working examples of these cocaine smuggling subs makes it possible to get a better idea of what the airborne heat sensors should be looking for. A snorkel, however, puts out less heat that a sub running on the surface would and is harder to detect. When running on batteries there is no heat to detect.