Drugs, People, Cars, Gold, Money, Smokes....That's my guess
Has anyone ever tried to 'hi-jack' one or these things? We could make a fortune...
You from Somalia or something?
I have seen containerships enter port with barbed wire still on the railings to prevent from being boarded.
Also some shipping companies hire security teams which are armed.
Plus the minor fact that the side of the ship is rather high and to get up there while at sea isn't the easiest thing to do.