It's a 2,000-pound cannon from Blackbeard's ship. The Queen Anne's Revenge wrecked in 1718 off the coast of North Carolina.
Researchers brought the eight-foot-long gun to the surface Wednesday. It's encased in a cement-like shell of sand, salt and barnacles.
The gun was on public display Wednesday in front of the state Maritime Museum in Beaufort before being taken to a laboratory for further study.
More than 280,000 artifacts have been recovered from the shipwreck since it was found 15 years ago.
The Associated Press contributed to this report.
