Identifying the Wreck
The most obvious damage to the mid section is the explosion damage to the after end. Approximately 10-15 feet of the hull is missing, starting just aft of the conning tower. The edges of the break are torn and tend to be bent outward, especially on the starboard side. The explosion that tore the hull plates appears to have occurred within the hull approximately where the scuttling charge was found to be located in the captured I-24tou, leading us to assume that the crew had managed to detonate the scuttling charge. The interior of the aft battery room has been completely cleaned out...the batteries, intermediate supports and crawlspace have mostly disappeared. Some battery cells are lodged in a section of twisted metal that extends farther aft from the lower quarter of the section's main body. The fact that these cells remain suggests that the interior was not plundered when salvaged; instead, the evisceration of the interior most likely was the result of the internal explosion, with dislodged debris spilling out the open end.
Since the wreck was first imaged in 2000, the twisted hull remnants extending aft have sagged to the ocean floor. The character of this break is a possible indicator of where the sub was when the scuttling charge blew. In an experiment designed by naval architect Roger Long, we found that with the model floating on the surface, the internal explosion vented upward, leaving the bow connected to the stern along the bottom. When the sub model was sitting on the bottom of the tank, the underside of the model actually ruptured, indicating that even given the shallow depth in our test tank, the water above provided more resistance than the sandy bottom. Comparing to the actual wreck, we conclude that the damage seems consistent with a detonation occurring while the sub was on, or just under, the surface. It was also worth noting that in both runs, the aft seam held.
Moving forward on the mid section, the conning tower had deteriorated much since 2000, when Terry Kerby of the Hawai'i Undersea Research Laboratory (HURL) first discovered it to be largely intact. In 2000, the extended periscope was entirely intact; in 2009, it was broken just above the fairing, with the lens control cable dangling in the current. The after fairing had completely fallen away and now lay on the bottom underneath the sub.
Since the sub is sitting at an angle on the bottom, Terry was able to visually confirm the lack of an access hatch in the underside of the hull.
No evidence of damage from an external source (e.g., the "washboarding" effect created by nearby depth charge explosions...that on I-22tou being a good example) was noted.
Forward of the conning tower, a hole was punched into the starboard side of the hull by a camera sled that accidentally struck the wreck in 2000 during the search for the Ward's sub. Over the years, the hole had enlarged and I tried to get a glimpse inside to see if the extra HP air tanks provided to the Pearl Harbor subs were visible. Unfortunately, the view was blocked by batteries that seem to fill the forward battery compartment. Another hole was punched into the upper hull plates close to the forward seam, and a steel cable was looped through this hole and out the open end of the seam. Since 2000, that hole has also grown larger.
The hatch on the forward bulkhead of the forward battery room was completely blocked by dislodged battery cells. This was another indication that the sub's interior fittings were not plundered before the wreck was discarded.
The seam flange on the forward end of the mid section is in similar condition to its mate on the bow section, with one notable difference...there is a deformation in the lower starboard quadrant of the circle that doesn't match the bow section. This indicated to me that the mid section was dropped roughly after it had been separated from the bow section. A portion of the flange in this area was scraped clean by Terry Kerby and we discovered that the severed bolt heads that once held the two sections together were still filling the holes. In other words, the fact that those bolts were still in place indicated that they had been cemented by marine organism concretion before they were cut. A sample of the scraping from the flange itself was sent to the Chemistry department of the University of Nebraska-Lincoln for analysis and they saw no concretion in that sample. Their conclusion was that a torch was used to cut the bolts, interjecting an oxygen-induced corrosion by-product that made for a poor substrate that would support biological growth. Taken together, our analysis determined that the interior of the sub had been flooded for a period of at least a few years before the mid section was separated from the bow. In other words, the sub had been completely sunk before it was salvaged.