[0] https://en.m.wikipedia.org/wiki/Narco-submarine
They have already taken several cell-towers, why wouldn't they add some fiber...
However, organized crime using unmanned true submersibles might [soon, or presently] be feasible. The expertise needed to actually attack a cable in a constructive manner would be a significant barrier to clear, but not inconceivable for crime organizations that can kidnap and coerce tech professionals. The ability to splice fiber underwater with a drone submersible seems extremely advanced though. I think only a few nations might presently have such a capability.
Nice summary of narco subs from HI Sutton: http://www.hisutton.com/Narco%20Subs%20101.html and https://www.youtube.com/watch?v=BR18qhnGEpM
I also learned from the YT comments that there is a theory that the Phoenecians might have crossed the Atlantic to South America, and that they might have brought back cocaine that was used by upper-class Egyptians. I expected this to be some kind of fringe conspiracy theory, but the Wikipedia page (https://en.m.wikipedia.org/wiki/Theory_of_Phoenician_discove...) suggests that anthropologists think it's totally possible, but lacking in actual archaeological evidence to support it. Cool!
I think your sense of geography may be off a bit.