H. I. Sutton’s Covert Shores has a short guide to the various types of “drug sub” smuggling vessels. He lists five types and provides photos and/or diagrams of each.
To some extent this is an advertisement for his book, “Narco Submarines: Covert Shores Recognition Guide,” but I think its worth a look. For some the book may be worth a look as well.
Chuck Hill's CG Blog 
I’m rather curious as to why the US Navy isn’t taking an “inspirational approach” too these Narco Submarines and Semi-Surface vessels. Here are the Columbian Drug Cartel producing working examples of what the US Navy “as to date” have been conceptualizing for decades as possible Future US Naval Ships…
He’s an excellent illustrator.
It is a very interesting web site. He looks at a lot irregular warfare systems that Port Security might be concerned about.