I'll tl;dr this:
This is a ship used by US special forces because it is a converted container ship so it cannot be readily identified visually. This isn't a huge threat to a nation with robust space/air surveilance network as they can just track it real time, but for a crumbling nation like Venezuela & associated cartels, that means that ANY cargo ship could potentially be ready to put into the air a drone, or a helicopter or drop a zodiac full of 28 Buff, Cool US Marines.
Externally it is identical to any Maersk freighter because it very literally is. This was what they used against pirates in Somalia. Supposedly there have been other internal modifications to enhance durability.
The guys at the docks are on edge because if its there, that means that the SEALS are there. And in fact that means the SEALS are probably already in-country, doing who knows what and OH MY GOD THEY ARE RIGHT BEHIND YOU! But also because they misunderstand the Ocean Trader; in theory, it can also carry a decent portion of a container ship's cargo (top deck) so it would mean logistics for a US operation, but the US has other auxilary supply ships for that (ones that are mostly converted to SecOps command)