question is a good one. I think I'd answer it in this way:
If I'm out of normal VHF
range, ( SSB
land ) in waters with few or no aids to navigation
and more than a days journey from a safe harbor I'd consider myself
" offshore". In that scenario the vessel and crew, would have to contend with whatever weather
and sea conditions developed for an extended period of time.
The further away from a safe harbor, the more likely you are to encounter a wide range of conditions.
That said, trying to run an inlet in a gale, would scare me more than riding it out at sea.
In your example, Florida to Maine
, much of that journey can be done either inside or near coastal. NJ to BVI is offshore, unless you go inland or near coatal to florida and Island hop. Still, you'd have to cross the Stream..and some of the legs are long, I believe. I don't have those charts
loaded right now.