...Are sharks really still so mysterious to people?

I love them, but I think we understand them fairly well at this point.

Indeed. While, yes, there is much more to learn, we know quite a bit.

Which is why I am wondering if bull sharks being able to swim upriver into lakes is really such shocking news anymore.

Some people think that means they are going to be in any river anywhere. They don't understand brackish water and how far that extends.