Researchers from the University of South Carolina's Institute of Archaeology and Anthropology have been off-and-on at the site of the former Confederate Mars Bluff Navy Yard since 2009. The cannons were thrown off the Pee Dee at this site. Mars Bluff Navy yard was one of about a dozen shipyards established inland, up rivers and far enough away from the Union ships along the coast for safety.
The cannons range from 9,000 to 15,000 pounds each and are between 9 and 12 feet long. One is a smoothbore Dahlgren the Confederates captured from the USS Smithfield which was sunk in North Carolina by the CSS Albemarle. The other two are both Brooke rifled cannons forged at Selma, Alabama.
The CSS Pee Dee was finished too late to see much action and its is not clear whether it ever fired a shot in anger.
This is bringing to an end a years-long archaeological effort, funded in part with a $200,000 grant from the Drs. Bruce and Lee Foundation in Florence.