The 12 inch Columbiad was available in those days. A giant among field pieces, usually used in shore batteries along the ocean or navigable rivers. http://en.wikipedia.org/wiki/Columbiad
If there was anything that size in Texas, which I don’t believe there was, it wasn’t anywhere near me.
The Trinity river couldn’t handle large boats, and it would take a large boat to handle something that size, so I doubt it was fired from a boat.
Just to get over the banks of the river and the trees you would have to fire it almost straight up from a boat on the river. I found it almost 3 miles from the river, so I don’t think it came from a boat on the river.
I doubt seriously they would commit a canon that size for small river boats they would use a smaller canon they could move.
I’ve wondered if the one leg Mexican Santa Anna had anything that size.