You are correct it does not add up. A team could easily take control of any one of these vessels. There is no reason to not do it since they are violating maritime law. Further, just where are they going to get the merchant seamen to willingly lay down their lives for Ol' Saddam?
Same place thay got airline pilots...
If they want to hide a mobile cargo, it will be on large trucks in Iraq, possibly in Syria if they have a deal. The USN owns the oceans, and even Saddam and OBL know it.