TERRORISTS IN SUBMARINES menace the Free World!
Pale, smelly peril of underwater cocaine 'Love Boat'
We know this because of the case of the French ex-spy and his speedboat-submarine factory in Dubai
A good indication of the best possible performance in this kind of tonnage range is offered by the specifications of the "Proteus" submarine speedboat formerly offered (and in one case built) by the now defunct company Exomos of Dubai. The Proteus, designed by former French naval officer, engineer (and reportedly ex-DGSE secret agent) Herve Jaubert2, used diesel-electric propulsion. Like the other Exomos subs a Proteus could manage five knots tops while submerged and travel as much as 50 miles at slower speeds of just a few knots before conking out.
Crazy old-school WWII style camouflage. Or possibly a case of designers sampling the product.
That's probably the upper performance limit for small submarines using today's technology: the Ecuadorean narco-sub is unlikely to be even that capable. The narco-boat would be able to move at a crawl fully submerged, and perhaps travel as far as 20 or 30 miles like that - but in fact this capability would be mainly for escaping from or eluding the notice of patrol boats and ordinary search aircraft, not for travelling. Almost all the distance covered on a mission would be done on diesels - as has always been the case with naval diesel-electric subs, in fact.
Interestingly, the Chronicle reports that the sub's structure is of wood and its hull of fibreglass. It's thus almost certain that it isn't a true pressure hull, but instead functions like a diving bell: compressed air is released into the interior as it descends, matching the increasing pressure outside and keeping the water out.
Such a vessel is much easier to build and much lighter than a proper pressure hull, though it means that the crew must observe the same precautions against decompression sickness ("the bends") as divers going to the same depth would. Buildup of exhaled CO2 while submerged could be handled by simply flushing through periodically with more bottled air (at the cost of some telltale bubbles rising to the surface) or the use of sodalime scrubbers - easily available nowadays as part of the rebreather apparatus popular with some sports divers, or commercially supplied for use in hyperbaric chambers3.
We also learn that the narco-sub is at least as uncomfortable for her crew as naval diesel-electric boats were/are: the periscope would have offered the only view out, and the vessel is furnished with a single toilet of unspecified type. "No apparent sleeping area or galley, but there is room to lie down", says the Chronicle. It would appear that the possible narco-smuggler or terrorist submariners of today and tomorrow are likely to be every bit as pale and unhygienic as their naval brethren.
So, would this sort of sub be useful to terrorists?
Theoretically yes. You could use it to sneak people in and out of target countries, for instance, or to deliver weapons or explosives, or to mount attacks on oil rigs or stationary ships (it would not be much use against ones underway, being too slow to intercept or keep up with them even on diesels).
But the DEA reckon it probably cost $5m to build. The narcotics cartels can find that sort of money, but they'd expect to make it back again - and more than back again. The little sub could carry cocaine that would be worth $100m at US retail prices, but of course its operators couldn't expect to get anything like that for a bulk delivery (most likely in Central America or Mexico rather than the States). It might well have required several voyages to pay for itself.
Terrorists with $5m to spend (especially with no real prospect of any financial return) seem to be extremely rare birds, and if they exist there would seem to be better things to spend the money on (it's a lot easier to attack a ship or oil rig using a helicopter than a submarine). But sure, if there are some wealthy and determined terrorists out there this is a potentially quite effective route to go down. You could easily blow up cruise liners, tankers, oil rigs, pipelines; you could mount Mumbai-style sub-borne commando raids in the heart of London or whatever - various Bond-villain style plots.