Did you guys see the Jeremy Wade episode where he was fishing for Bull sharks in Natal, South Africa? They're called the Zambezi shark there, as it swims up that and other large freshwater rivers.
He caught a big one, over 13 feet, which is longer and heavier than any caught so far in the ocean! And because he was part of a shark research program at a university there, he had to release it, to the shock and horror of many people living by the river and who swim in it!
The Bull shark (C. leucas) is among the most often implicated in attacks on humans, and does enter fresh water in North America.
I have a shark book that lists max. length at 11.5 feet, so the one over 13 feet caught by Wade is really impressive! It might be a world record! But more that size are probably there, yet uncaught. Sobering, if those sharks swim near you...and they do, if you live along the Amazon, the Mississippi, and other large waterways. Or on Lake Nicaragua.
T-Star