They planned to enter the Hunley Monday through a 3-foot hole in the rear starboard quarter of the submarine, said Bob Neyland, manager of the Hunley Project.
The Confederate sub was a 40-foot hand-cranked experiment, fashioned from an old steam engine boiler. On a cold starry night in 1864, it rammed a black-powder charge at the end of a spar into the side of a Union warship.
It became the first submarine to ever sink an enemy vessel, a feat not repeated for another 50 years. But it mysteriously sank as well. The South's secret weapon became the South's long-missing coffin.
"Those hatches were sealed on February 17th, 1864, and they haven't been opened since then," says historian Mark Ragan. "Everything that was taken on board that night is still in there."
The submarine was raised last summer and brought to a conservation laboratory at the old Charleston Navy Base.
The sub was kept immersed in a tank of cold water while scientists mapped the hull and determined the best way to enter it.
Sunday, about 250 people, many of them wearing Confederate uniforms, gathered for a memorial service for the crew. The invitation-only service was for the volunteers who have given tours of the lab and done other volunteer work for the Hunley recovery.
The crew's remains are expected to be buried this year in the Hunley plot in Charleston's Magnolia Cemetery, next to members of two other ill-fated crews.
The submarine sank twice before the Housatonic attack once while moored at a dock and once on a training mission.
After the excavation, conservation of the hull is expected to take several years. The Hunley will then go on display at the Charleston Museum.
©MMI Viacom Internet Services Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report