As an exercise, wouldn't you learn more by finding where the most ferries are and studying how they compete with one another and try to find a niche that can be exploited? changing costs, better production of boats, changes in demographics, infrastructure issues, politics, environmental concerns- these things drive trends. An underserved area would need all new infrastructure most likely, and you would have to create the demand. And there isn't any such thing as a profitable transport market that isn't being served in some capacity, but perhaps not very efficiently. A cursory look at what is required to actually own, licence and operate a ferry vessle would be prudent as well.
Martha's Vineyard? Not a bad place to study ferries.