That was a spar torpedo - basically a long wood pole with an
explosive charge on the tip. A lanyard was attached to the
explosive which allowed attacking boat to get free before
charge was detonated.
That is what has been repeated and that is what we have been led to believe, but in actual fact this is not true.
Sometime Last year we were discussing the Hunley, and a man who had taken part in the actual research on the vessel posted pictures that show the spar torpedo was bolted firmly to both the Hunley and to the Copper clad explosive charge. They were relying on the 20' of spar (which I believe was made of iron) to protect themselves from the explosive, but they didn't realize that the force transfer would be greatly amplified by the water and the iron spar.
The man posted actual images of the relevant parts recovered form the Hunley, and it appears he is absolutely correct. There was no lanyard. They rammed the ship with an explosive on a 20' long iron spar and the charge was rigged to blow on contact.
That's why the Hunley sunk. All the men on board were killed instantly. Their brains were jellied by the concussive blast.
This information is still somewhere here on Free Republic, but I have forgotten the name of Freeper who posted it. I could dig back through my own messages, but it would take me a very long time and I would rather not do it.