Not to take away the importance of the discovery or of the history of this machine; but to ignore the accomplishments of the Hunley or it's influence in the building of this submarine is lame. The "Explorer", the show plainly shows, was an navigable diving bell. With a motor(man powered like the Hunley)system that had only one person powering it, bulky hull, and relying totally on ballast to raise and lower it, it was no doubt a very slow craft (an obvious fact the show does not point that out). The uniqueness of the "explorer" is it used compressed air and a double hull for raising and lowering the craft (the same as diving bells of the time). The Hunley used hand pumps and DIVING PLAINS to dive and surface; the Hunley was built for speed with over a half dozen men powering it.
As of yet, no one has proved it was a design flaw that sank the Hunley. The evidence is more in favor that it sank due to damage in combat. So to claim the "Explorer" was the first successful submarine or even first successful deep diving submarine is dubious since the show revealed all the crew died- from most likely the bends- caused by the design flaw of using the combination of the use of compressed air and ocean pressures at depth.
http://www.smithsonianchannel.com/site/sn/show.do?show=136074
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David Upton