The term "offshore" is a loose one that varies in meaning from place to
place and between different people.  That said, it generally refers to
localities several to many  km/miles from shore, in deep water - as
opposed to the "nearshore" zone where small fishing boats venture.  The
"Offshore" fishery is generally pursued with large, open-ocean capable
vessals, and can be up to 1000 fathoms for deep-water trawling.

From balmy ol' New Scotland, enjoying a late-summer warm spell,
-Ross M.