Those ships are fairly easy to board. They probably just drove a boat up and snuck on. Might have had inside help.
I too am thinking inside help.
A lot of the longshoreman in that part of the world are pirates. In Viet Nam some of the longshoreman were VC.
Sri Lanka we observed and praised the physical prowness of a longshoreman climbing just wires & toe holds up five levels of containers on the stern of the ship ahead of us. The pilot bringing us in said those are the same guys that would board us as pirates.
Desert storm we were on high alert for terrorists boarding us in Asia. In one port they “doubled the guard” by putting grinning idiots leaning hands & face on their ancient shotguns while their cohorts looted the containers.
Inside help indeed. Al Quada infiltrated longshoreman is my guess.