The whole matter of size is somewhat overrated (no jokes please). When I first left school I served an apprenticeship as a boilermaker at a company which made road tankers. You know those things that carry gasoline, or oil, or chemicals.

Many of them were a lot smaller than the Hunley but we could work inside them easily (and I'm 6'-2"), even the little ones that deliver your fuel oil. The smallest manholes were elliptical and were 16" by 12". No one had any problems getting in or out of the tanks.

Not to say that those Hunley guys weren't brave, because they were. Just that there was a reasonable amount of room inside.

Bert.