I don't know about the boat scenario, but I attended the local Dallas Fort Worth ANA meeting last weekend, they invited a vestibular therapist to the meeting.
She was really great explaining the mechanics of balance (the role of the eyes, the inner ear, and sensation in your joints - all of them factor in). She showed how a good therapist can identify very specifically where your system is not quite working right, and give you a simple tailored exercise plan that takes just minutes a day, to "train your brain" to adjust for the new you.
I think probably some people don't realize they need more time w/ specifically a vestibular therapist, or maybe there isn't a good one locally. Anyway seems like they have a whole lot to offer. But patients need to know about it and seek it out. I think it is covered by most medical insurance.