You have said you are just looking for a ride between islands. In the BVI, that means 2 to 6 hours, most if not all of it on deck. You won't be using a berth, or spending much time below, but even if you were, your height is irrelevant. I'm 6'4" and have a couple of dozen Caribbean charters in my past. And the US Navy upper height limit for submariners is 6' 8", so you are good to go!