It's really interesting that 45 vertical ft of silt can pile up on top of something in 150 years.
> The snag ripped open the hull, which rapidly filled with water. The upper decks of the boat stayed above water, and the only casualty was a mule that was tied to sawmill equipment and forgotten. The boat sank so rapidly into the mud that by the next morning, only the smokestacks and pilot house remained visible.
Since two decks disappeared overnight, that suggests the boat sank at least 15 feet into the mud.
We can assume the water depth was that of the hull and the first deck, but I can only come up with a wild guess that it's between 10' and 30' of water which later became silted over.
Most suitably large construction digs will turn up something of archaeological interest.
"'Entire streets' of Roman London uncovered in the City": http://www.bbc.com/news/uk-england-london-22084384