I wouldn't exactly call that thing a submersible. Especially since they have all these open exhaust vents that can take on water. It looks like a knocked down cigarette boat with an ultra low profile to avoid visual and radar detection to me.
I would not be surprised if at some point a diesel submarine that used to operate in former Soviet or Chinese control turned up transporting drugs for one of the cartels. Then you have to find the transfer point and the boats running from the sub into shore and that would be an extremely difficult operation at best.
Yea I know they aren't subs in the classic sense, they are just low profile custom boats. However one of the first subs was the US Monitor from the Civil War which was of similar design and was considered a sub even though it didn't fully submerge.
As for the Russian Sub's deal and the Drug Cartels, well that was tried and the guy was busted. If you ever saw the movie Lord of War it was loosely based around a real arms dealer that got busted for doing just that. He had a deal set up to sell one of the old Russian subs to one of the major Drug Cartels and it was going to be staffed with the old Russian crew. This was back after the USSR first collapsed and none of the military was getting paid.