The pattern of damage of the holes was determined to have been caused by a combination of galvanic corrosion, stresses from riveted seams, and erosion from ocean currents. These strata indicated that the holes were not present during the vessel’s initial time underwater. The holes were determined to have occurred at a later date because analysis of the types and quantity of sedimentary materials, including marine macrofauna, showed strata of sediment deposition that permitted analysis of the general patterns of sediment accumulation over time within the hull.

The two large holes discovered in the bow and side of the hull were determined not to be the cause of sinking by analysis of the sediment layers within, which showed that both breaches occurred long after the sinking, and no additional damage was found to the hull that provided an explanation. The keel ballast weights, which could be released from within the boat, remained firmly attached. The bilge pumps were not set to pump out water. The conning towers, which formed the only path of escape, were closed with the aft tower still securely locked. The skeletal remains of the crewmembers were found seated at their respective stations, with no physical injuries or apparent attempts to escape. The Hunley was raised from the ocean floor in 2000, and conservation efforts have been ongoing since. At the other end of a hinged 16-foot spar was firmly bolted the Hunley’s torpedo, a copper torpedo of the common Singer’s design type filled with 61.2 kg (135 lbs) of black powder and fitted with a pressure-sensitive trigger ( S1 Fig).

The vessel’s commander could see out the fore conning tower and was responsible for navigation, while the remaining crewmen powered the vessel’s propeller from the inside using a hand crank. More renderings and details of the construction of the Hunley can be found at. Image courtesy Michael Crisafulli of The Vernian Era. The HL Hunley as it would have appeared in attack position on the evening of February 17, 1864.

1800s submarine drawing