Yeah, bull sharks are the most common and wide-ranging of the sharks that are adapted to survive in a wide range of salinity levels.

Bull sharks are often found in rivers tens of kilometres from the ocean in Queensland.

That's the kind of rare and highly luck based curiosity they ought to give you a plaque for. "From this shore in 1973 local angler..." Slap it on the same sign post as the flood high water markers they put up.