There is a new publication that appears to be the definitive source on Narco subs and related craft including semi-submersibles and un-manned, towed narco “torpedoes.” It certainly has the best selection of photographs I have ever seen on the subject.
Narco-Submarines Specially Fabricated Vessels Used For Drug Smuggling Purposes
In cooperation with InSight Crime & Small Wars Journal— El Centro
Byron Ramirez and Robert J. Bunker, Editors
And of course these could be used for smuggling in things other than drugs.
You can access the report in pdf form here.
Chuck Hill's CG Blog 
Who builds these things? And where?
It is all in the report. Kind of amazing they build these things mostly in the Jungles of Colombia and Ecuador.
They probably do not meet OSHA standards.
“They probably do not meet OSHA standards”.
Lol. That was funny.
I started reading the report, it’s long, so I got lazy and just thought I’d ask. I’m going to read it when I have the time though. It’s amazing to me that they can and do build these things.
I was really surprised at how much is transported by these subs. It’s a significant percentage.
Maybe an argument could be made for the Coast Guard looking into Captas 1.
The build up of subs in the Russian and Chinese navies, the narco-subs, and the possible use of something similar by terrorists, all suggest maybe it is time to bring back the ASW mission. Or at least make sure we can bring it back when it is needed.
Another one down. http://www.cbp.gov/newsroom/local-media-release/2016-03-24-000000/cbp-p-3-detects-semisubmersible
Notice, this is a two day old CBP news release. This never made it to the “Coast Guard’s Digital Newsroom.”
Probably because it is outside the normal purview of the districts.
Five semi-submersible busts in a year after one in 2014 and none for the previous two years. http://www.navytimes.com/story/military/2016/03/28/coast-guard-cutter-busts-fifth-cocaine-sub-less-than-year/82346182/