Hi Mr. McCollum,
The answer to your question depends, it can be as close as 7 miles out to over 100. It all depends on many factors.
The migration of Bluefin Tuna in the Brunswick, Georgia area usually runs from around December to February. A lot depends on the water temperature. The ideal is 60 to 68 degrees. If there is a prolonged winter or summer the migration could be sooner or later by a week to a few weeks.
What I would do is contact a local tackle shop in that area and ask them the name of the local Bluefin Tuna expert, in five minutes he can give you advise that will be invaluable.