I'm considering the case of what several 10" or larger holes would have achieved. Ft. McAllister, as well as the rest of the Southern ports of interest to the Federals, was underarmed is my point. Creative improvisation could have provided the firepower necessary for successful defence.

You state that the effect of the torpedo on the U.S.S. Montauk was as if being holed by a 10" Mortar round. The vessel beached herself immediately; had she not the benefit of shoal to beach she would have been on the bottom and subject to salvage. Multiply the effect as if by barrage. The time factor for damage control becomes too slim for survival of the flat-bottomed vessel.

A sea turtle or shark in the area detonating the mine is not far-fetched. Both critters inhabit the area and both, for whatever reason, head towards areas affected by low frequency noises. The damage incurred does not match a direct hit. I've searched for a reference regarding the laying of the torpedo field and came up empty. Any knowledge on that one, Shawn? Wet powder would explain the reduced damage.

Small arms fire from the elevated position of Ft. McAllister or the opposite bank could have had enough inertia to dent the lead swaged tube that held the glass vial of acid used to detonate the torpedo at 8 to 12 feet depth. .577 Rifle round is a respectable chunk of lead.