Modern merchant vessels are already highly automated, to the extent that crew compensation is a fairly small component of total cargo costs. Trying to reduce the crew further would be chasing diminishing returns. While it's possible to build a vessel that navigates itself from port to port they will at least need some engineers on board to fix equipment when it breaks. It wouldn't be safe to leave a robot ship drifting powerless in mid-ocean. The crew is also able to do a lot of routine maintenance during transit. Without a crew, the ship would have to spend longer in port just to have enough maintenance time.

Interesting point. Automation will only continue as long as we can save significant amounts of labor by automating. So we can expect to see more automation in the construction of automobiles and lawn mowers, but in all likelihood the fabrication of microchips is about as automatic as it will ever get.

To be honest I imagine that a robo-shipping vessel would be easier to create than robo-trucks. for several reasons:

* The ships are larger and more expensive and hence the add on expense is smaller, comparatively

* There's less traffic around and the traffic that is around is likely to have on board beacons, etc

* The ships already have more sophisticated instrumentation than trucks (radar, etc)

Also, I would imagine docking would be the hard part. You could have a local human crew take over that part, perhaps.

That's already done. Most large ports require a licensed local pilot to board each ship and guide it in and out.

But there are also vulnerable to piracy.

Big cargo ships are already vulnerable to piracy and the handful of crew on board does little more than give the pirates some hostages.

If the ships were fully automated, and remote controlled, you could simply refuse to comply with the pirates and just keep sailing wherever you planned.

Under the assumption that the pirates could not compromise the command and control system, or simply cut the rudder and steer the ship manually.

But yes, it was these points that led me to suggest robot ships.

Because sealing the thing would cost a lot more money. Containerised shipping is all about reducing overall expense.