Mark Twain used to say that he was a better man than George Washington, because Washington could not tell a lie, but Twain could, and wouldn't.
I think everyone knew ten years after Twain was first published that Mark Twain (which means Two Fathoms of water) was a pen name.
Mississippi riverboats had a very shallow draft, because the depth of the river varies quite a bit. I was surprised that the riverboats on the Uruguay and Paraná Rivers in South America were not flat bottomed, even though these rivers (which are wider than the Mississippi where I was, are also somewhat shallow. Not as many snags, though.
Some Amazon riverboats are more like Mississippi steamers.