Equipment assembly error

I have a Transpac II. I use it because I frequently alternate between cave dives with double tanks and ocean dives with single tanks.

Two weeks before this dive, I had been spearfishing in the Gulf, using the Transpac and a single HP 120. When I got home from work on Thursday night, I pulled the single tank straps off the Transpac rig in preparation for diving Friday in Ginnie Springs.

Friday morning my wife and I arrived at Ginnie Springs about 9:30 AM. I met my cave dive partner in the dive shop, and we planned a first dive to the white room. We drove to the entry point, and got our gear out for assembly.

The Transpac consists of a harness with a small plastic plate and a wing. The harness has webbing for the insertion of two tank straps when diving with a single tank, and 6 grommeted holes when using double tanks. The rec wing I use has slots to allow the tank straps to pass through the wing, and 6 grommeted holes when using doubles. There are two plastic nuts and bolts connected through 2 of the grommeted holes to keep the Transpac harness and wing together for convienience when no tank is attached. They are not designed to be load bearing. When tanks are attached, either the tank straps through the harness and wing or the bolts of the double tanks through the grommets of the harness and wing are used for structural attachment.

I had not put the doubles on the Transpac in about a month. I bolted the doubles through the wing grommets, but failed to also push them through the harness. The tanks and wing were now attached to the harness with the two plastic nuts and bolts. I finished gearing up and started the walk to the entry point with my buddy. My wife mentioned that my doubles looked lower on my back then normal, but I didn't think anything was wrong so proceeded to the water.

Once in the water, I completed a bubble check and S drill without incident. The tanks felt a little "loose", but I chalked it up to having gone a month since my last dive with them.

We entered at the eye, and I ran the reel for practice. My tanks shifted around on my back much more than I remembered them doing, but I continued on. I tied the line off, and my buddy and I continued on. We went through the lips, and I was thinking to myself that my trim had gotten very rusty. It seemed that I was fighting a roll to the left, then one to the right continuously. My buddy later said that my tanks didn't look flat on my back. He motioned for me to slow down for a bit, and he looked over my gear. He didn't see anything obviously wrong, and we continued on.

By the time we got to the keyhole, I felt very uncomfortable. I was having trouble keeping the regulator in my mouth, and reaching my inflator. Apparently by this time the lower plastic nut and bolt had actually pulled the grommet out of my harness, and the tanks were starting to float away from my lower back.

At that point I turned the dive, and we started out. The rear of the tanks were now facing the flow of the water, and the tanks were pushed up almost vertically from my back. The upper plastic nut and bolt snapped, so the only thing holding the tanks and wing to my harness was a small strap used to position a single tank on the harness. I was proceeding on, but my dive buddy saw how seriously disconnected my gear was. He could see that I would have very serious problems exiting with my gear. He motioned for my to lay on the floor behind a ledge, out of the current. He took some line off his safety reel and attempted to tie the lower end of my tanks back down to my harness. He managed to get the tanks back down, though they were skewed to the right. We then exited the system. Once on the entry platform, we discovered the serious error I had made in assembling my gear.