Maybe we need a new top level category for autonmousness but here's this for now. I think the simplest way to get an autonomous boat across the Atlantic is to throw a bottle into the sea. Or a log. These guys have been trying to do it with model sailboats. And they have found out that "It’s just a really challenging environment". Something our friends making self driving cars should think about. But then programmers are full of hubris, aren't they? See:
http://www.bbc.com/future/story/20171115-can-an-autonomous-sailboat-cross-the-atlantic
Regards. J
http://www.bbc.com/future/story/20171115-can-an-autonomous-sailboat-cross-the-atlantic
Regards. J