sorry to disappoint you but there is a strong colony just off the coast not out on the reef on the 20 ft drop off on the sandy beaches just south of townsville been there for at least known over 100 years. when monofliment nets were introduced in the seventies instead of nylon cord wasn't uncommon to have fiffty dead ones in a night pro fishing
there are plenty off Double Is. point....Wolf rock is a diving spot famous for the grey nurse. it's a tad further north than Bris.
I may be wrong (not that that has ever happened before!) but I always thought grey nurse sharks migrated north in the winter to about as far north as SE Qld area? In summer I have never seen any grey nurse sharks off the coast in SE Qld, this time of year there are many.