It depends, small blacks get very close (4-5 miles offshore) sometimes, blues are mostly very far out.
This capture was about 35 knots off port but only about 20-25 knots off the nearest land. The location is about 200km (125 miles ) north of Sydney. We towed the boat there the night before and fished the following day, we knew the fish were there . This is an annual thing about the same time of the year. On the day we were out at least another 150 boats were there some from as far as 600 miles, almost all boats hooked fish, I would say 99% released to fight another day.