Wow! Now, I'm being attacked, asked if I'm being stupid and accused of painting DIR divers as idiots.
I find history interesting. I find the history of the underwater world in the form of shipwrecks and archaeological sites interesting. I find the history of diving equipment and diver training interesting. I find the evolution of diving and DIR interesting.
I asked the question simply to set up one of the things Bob Sherwood explained to me about the Britannic expedition and one of the reasons why steel tanks are not just for cave diving where you can crawl/pull out of the cave. I recall arguments in the past about the drysuit balancing the rig among the DIR cadre, and if IIRC somewhere in the G-isms there was something about drysuits not being thought of as redundant byouancy at the time. Which is why I asked the board. Aluminum tanks are still preferred in open water, even with drysuits, over steel.
Bob and I wreck dive dry with AL tanks. One night, at his fire pit, Bob and I were discussing steel tanks vs. aluminum. Bob explained that the buoyancy characteristics of the tanks did come into play on Britannic. It wasn't solely about the gas. If the team really needed the gas, they were some of the top divers in the world, and could have handled additional bottom stages if required. However, it was the buoyancy characteristics of the steel tanks with the incredibly high helium level for that depth that made such a dive fit all philosophical parameters that DIR strives to accomplish. Basically, the tanks would handle not much differently than the AL tanks. While jon lines are not normally DIR, in that case on that dive they were employed due to the long hang times and the current to help safeguard and reduce the fatigue levels of divers who were getting quite bored.
My point about Kool-Aid was going to be that JJ often posts that the parameters of any DIR dive may dictate certain courses of action. In this case, the divers determined the strategy based upon the needs of the divers. They gave themselves permission to use jon lines and the choice for steel tanks was not made just because they were allowed to wear steel tanks with drysuits. The needs of the divers and their safety in the environment was the major consideration. The seas were very high, but they needed to dive to make the production happen. It added some risk and challenge, but one the team was willing to accept. They didn't need to wait for the memo. They drafted it themselves.
Most of you are probably good divers with experience and training outside of DIR itself. As DIR divers, isn't accepting the dictates of others, at times, much like a trust me dive? The more experienced a diver, the better a diver can look at changes in DIR procedures and determine if he or she or their teams should really adopt them. Just because something is correct today, doesn't mean that it was changed for the benefit of the diver, but may have been changed for other, less noble, personal or liability reasons.