I would add to your article about deterioration of a wreck. I have been fortunate (lack of penetration dives) that I have yet to have a collapse occur. A friend of a friend went diving on a wreck the lies upside down in Lake Huron but has never been penetrated before, found a way into the bow cabins. His bubbles hit the ceiling (floor) and tons of lumber fell in on him in 230ft of pitch black water. He was a very experienced diver and he dropped his bottles and line and took about 5 agonizing minutes to escape the wreck. When he got out of the wreck, he only had 1300psi left in his db hp100's with 20-25 mins of deco and no deco gas (because they were inside the wreck) and he sucked the tanks dry after 16-17 mins from his ascent. When he got back to the boat, he grabbed one of his spare tanks filled with O2 and spent 10 mins at 15ft. He has not dove tech in the lakes since. The next day his partner dove where the collapse occured and the line that he was using showed that he went under the pile deeper inside the wreck and U-turned back out in zero vis. This story has always played with my mind when going inside wrecks, and I do not believe that I will do real tight penetration in deep wrecks. Thanks for the article.