By Tobias Carroll Dig deeply enough in any given place and you’re likely to learn something about the history of that particular region. The same is often true for bodies of water, and in the United States, the Savannah River has obtained something of a reputation for something lurking underwater there. This isn’t marine life or undersea vegetation, though; instead, the Savannah River is home to a host of Revolutionary War-era cannons. Smithsonian Magazine has more details on the latest discovery made there, and what it might mean. Last year, three cannons dating back to the Revolutionary War …