It's a good question - I suspect that there's no specific rule across vast areas as there is with roads and trains. Undoubtedly some boats would have been built to be very specific to their environment, but since the needs of the people making them varied as much as the places they'd be used I doubt there's a similar correlation. That said, I want a river boat as, although my girl can navigate some rivers, being as she's got a 30ft mast bridges would become a major issue.