That is a way harder problem than automated sailing.

Also a way harder problem than just designing in longer service intervals.

Honest question. Have you ever been in the engineering spaces in a ship/offshore rig/etc.? Do you have any idea of the diverse type of work a ship's engineer and his various reports do?

I don't mean to pick on you too much but the idea that you can have little Hueys, Deweys, and Louies tooling around a container ship doing whatever maintenance is required is ludicrous.

And the other suggestions about having crews that you transport from ship to ship isn't quite as unrealistic but is needlessly complicated in the way that software often is. Among other things--have the people suggesting this sort of thing ever been in the North Atlantic in bad weather?

That or have a small service vessel that sails with a school of autonomous ships handling maintenance.