Experts looked at the Hunley's lantern, but found no evidence of blue glass.
"I think it was just Dixon's flashlight, to be honest," says Mardikian, the conservator.
One scenario holds that the Hunley was swamped by or struck by a Union vessel. Or that it plunged to the sea floor to avoid detection, and never made it back up. A latch on the forward conning tower was found to be not properly locked.
In January 2013, Hunley scientists, who work for the Clemson University Restoration Institute, reported a significant discovery.
"Until now, the conventional wisdom has been the Hunley would ram the spar torpedo into her target and then back away, causing the torpedo to slip off the spar," they said in a statement.
Instead, research showed the submarine was less than 20 feet from her torpedo when it exploded.
"There is overwhelming evidence to indicate this was not a suicide mission. The crew no doubt knew the dangers facing them, but still, they hoped to make it back home. They must have believed this was a safe enough distance to escape any harm," says South Carolina Lt. Gov. Glenn McConnell, head of the Hunley Commission.
It's possible that the force of the explosion incapacitated the crew, eventually causing the sub to slide down into the chilly depths. Even a small hole or holes could have allowed water to seep or pour in.
"Everything we have tried to explain (as to) how the submarine worked, we were naïve in our approach," says Mardikian.
Researchers at the lab, while excavating the sub's interior silt that held the the human remains, found the eight Hunley crew members were still at or near their stations, despite an unsealed forward hatch.
"We don't see evidence of anyone trying to get out of the submarine. It could have been something catastrophic or they died with a certain amount of resignation," Neyland says.
Detailed examinations of the well-preserved remains of the crew looked for the tiniest of fractures or evidence of concussion. "We did not find any unhealed injuries to their skeletons," says Scafuri, the Hunley Project archeologist.
The team is still gathering and analyzing data on the physics and effects of the detonation on the Hunley and its doomed crew, he says. It also continues to analyze the source of holes in the hull, possibly from battle damage or exposure to currents and underwater conditions.
Ongoing efforts to learn more about sub, crew
In 1995, the Hunley was finally located by a group led by author Clive Cussler. It rested in several feet of silt, largely protected from strong currents and the most corrosive effects of saltwater. The environment, mostly free of oxygen, left the skeletal remains and artifacts in amazing condition.
The submarine was brought to the surface five years later and was quickly placed back in protective water at the Lasch laboratory.
The federal and South Carolina governments have contributed an estimated $9 million or so between them on the recovery, lab and research. The Hunley, considered a spoil of war, is the property of the U.S. Navy.
About 40,000 visitors a year marvel at the Hunley, see exhibits and peer at facial reconstructions of the crew members.
Researchers found personal artifacts, including a wallet, watch, bandana, matchsticks and remains of tobacco pipes.
One mystery was answered relatively early in the excavation and conservation process.
"They didn't know whether these guys had escaped and tried to swim to shore," genealogist Abrams says of the Hunley crew. "Or whether they had been taken captive. There was no concrete knowledge that they were still inside."
Inside the sub, scientists found human hair, complete skeletons and skulls of eight people -- debunking one part of the legend that held that nine men were on board.
Abrams has spent years trying to learn more about the crew. She has learned a great deal, but is hampered by the fact that only one is known to have married and have children. And there are no known photographs of any.
Kellen Correia, executive director of Friends of the Hunley, says she expects a permanent museum to be built around the end of the decade, with expanded days of operation, instead of the current weekends.
For the anniversary of the attack, the first 150 visitors on Saturday and Sunday receive free replicas of Lt. Dixon's gold coin, which is on permanent display. Admission on Monday, the actual anniversary, is $1.50, compared to the normal $12 ticket.