That’s the setup for an old joke. It goes something like, “The absent-minded maestro was racing up New York’s Seventh Avenue to a rehearsal when a stranger stopped him. “Pardon me,” he said, “can you tell me how to get to Carnegie Hall?”
“Yes,” answered the maestro breathlessly. “Practice!”
For technical divers, practice is no joke. It may be cliche to say that sharp skills can save your life, but it’s true nonetheless. More importantly, sharp skills may defuse potentially life threatening situations before they escalate.
During training, technical divers are drilled in basic drills like manifold shutdowns, gas sharing, SMB deployment, regulator malfunctions and many others. When you are a student, it’s easy to view these skills as hoops to be jumped through in order to pass the course. The true value of the exercises can be lost. The importance of these drills doesn’t end when you get the certification card. It’s important to maintain competency. The goal is to practice each skill until it can be performed comfortably and easily. When something unexpected pops up during a dive, say a free flowing deco regulator, you should react calmly and automatically. You should react as if you’ve done this a hundred times before because you have done it a hundred times before!
Skills are perishable. Just because you could deploy an SMB perfectly 2 years ago doesn’t mean you can do it today. You have to practice regularly to maintain proficiency and build muscle memory. Now is the perfect time to review your skill set. As the dive season begins, many divers are getting back in the water at local lakes and quarries. Dedicate time on each dive to review and practice. That way, by the time the dive season gets into high gear, you’ll be ready for more challenging open water dives.
The basic tech diving skill set is not only meant to avert life-threatening situations, but also to build confidence. Divers who practice on a regular basis can perform better in the event of an “unplanned event” during a dive. Knowing you can handle most any contingency results in a calmer, more relaxed dive. So as you get back in the water after the winter break, practice your skills, dive safely, and have fun!
In my last article, I discussed the use of personal dive computers and the absolute necessity of carrying some form of back up decompression tables. I referred to the practice of generating decompression tables using software such as V-Planner and then writing the deco schedule in a waterproof notebook. In the past week, I’ve received a couple e-mails asking for more information about this practice. Apparently since the advent of personal dive computers, carrying handwritten back up tables has faded. Here’s my approach. Take it for what it’s worth.
As I noted in the previous article, personal dive computers for technical divers are a fairly recent development. When I got into technical diving in the 90s, the accepted standard was to calculate a decompression schedule for a specific dive using desktop computer software. Back then we used Abyss or Decoplan. Once V-Planner came out (around 1999 I believe), many of us switched to that and have used it ever since. Once a deco schedule was computed, it would be copied by hand into a waterproof notebook. At that time, the gold standard was Richie’s Wetnotes. Since then, many other manufacturers have come out with waterproof notebooks of their own and the term “wetnotes” has become the generic term for any such book (much to Richie’s chagrin I’m sure). The reason these notebooks are waterproof is that the pages are not paper, but thin sheets of plastic. I carry mine in my drysuit thigh pocket.
When developing a dive plan, I start at my computer. I open V-Planner and start running various permutations of my plan. For a Great Lakes wreck dive, I usually know the depth and start with a bottom time of 20 minutes. Then I start fine tuning the variables. What if I use X for bottom gas? What if I use Y for bottom gas instead? How does changing deco gasses affect the plan? What happens when I vary bottom time? This process can be an article or two all by itself. Since we’re talking about how I use a waterproof notebook, let’s fast forward to the point where I have a viable dive plan worked out. I also work out a couple contingency plans. You can go crazy with contingencies. You can make plans for staying longer than expected, shorter than expected, deeper than planned, shallower than planned and plans that account for lost deco gas. You can come up with more contingencies than pages in the book. You have to decide which plans are worth carrying with you. Neatly write the plans you want to take with you in the notebook. I usually write the deco schedule for planned dive, a five minute longer bottom time and a 5 minute shorter bottom time. You, of course, can make as many or as few contingency plans as you like. I write them neatly with a fine Sharpie, clearly identifying depth, time and gas mixes used. I do this because this notebook becomes a permanent catalog of dive plans.
When you write plans in your book, you can use either stop times or run times. Stop times are pretty straightforward: stop at 90 feet for 1 minute, stop at 80 feet for 1 minute, stop at 70 feet for two minutes and so forth. Run times refer to the total elapsed time of the dive. For instance, on the plan pictured above for a 20 minute dive to 190′, I would leave the bottom when my timer reads 20 minutes and make a slow ascent to 90 feet. When my timer reads 24 minutes, I ascend to 80 feet. When my timer reads 25, I ascend to 70 feet and so on. The benefit of run times is that it eliminates the need to do math at your deco stop (looking at your timer, looking at your schedule, adding the stop time to elapsed time). However, for run times to work, you have to be on schedule. You have to leave each level at the proper time. If you leave the bottom at 23 minutes instead of 20, your whole run time schedule is off.
After a couple years of diving, you’ll probably have about every profile you’re likely to need written in that book. It has become your analog dive computer. Even if the dive plan changes, you’re pretty likely to have the appropriate schedule, or something close, in your notebook. I’ve shown up to the boat only to find that our destination has been changed because of weather or some other reason. While others are scrambling to warm up their notebook computer (or tablet, or phone) to cut new tables, I just have to flip through my “analog dive computer” to find the right deco schedule for the new depth.
I’ll admit it. I like planning dives. I like noodling around on V-Planner with different scenarios. I’m also pretty uptight about having back up plans and back up plans for back up plans. I use a personal dive computer on every dive. But I also have my notebook in my pocket with plenty of back up schedules. Maybe carrying a notebook full of dive plans isn’t your style. That’s fine. Just be sure you have adequate redundancy and back ups. Technical diving is all about the odds. I try and stack the odds in my favor on every dive. Dive safely.
Not that long ago, there weren’t any personal dive computers (PDCs) for technical divers. No PDC that could handle multiple gasses. None that could compute a decompression schedule for helium-based gasses like trimix. Back in those dark times, we planned our dives using desktop computer programs like V-Planner, Decoplan, Abyss or something similar. We copied the deco schedules onto slates or into waterproof notebooks (including a few contingency plans). We executed the dives using these tables and a simple bottom timer to track depth and time.
Fast forward to the present. Now we have a choice of high quality, reliable PDCs for technical diving. PDCs that can compute deco schedules using multiple gasses, including trimix and other helium-based mixes. One of the warnings that emerged as technical PDCs gained popularity was that computers make divers lazy and overly dependent on technology. What happens if the computer malfunctions during a dive? The reasonable answer is that using a computer does not eliminate the need for redundancy. Even though we may be carrying a high tech PDC, we still need redundancy in the form of another computer or printed tables.
Unfortunately, it’s too easy to get sloppy and not follow proper procedures. After conducting numerous dives using a PDC, it’s easy to get lulled into a false sense of security. That can be dangerous. It’s usually when we feel safest and invincible that Mr. Murphy pays a call. No matter how reliable your PDC appears, you need to have redundant methods of computing your ascent schedule. You probably still use software like V-Planner to pre-plan your dive. Take the time to write an ascent schedule and a couple contingency plans in your waterproof notebook. Contingencies can include deco schedules for 10′ deeper than planned, a few minutes longer than planned, as well as shallower or shorter than planned. As a last resort, you could even use the good old US Navy Air Deco Tables to figure out a reasonable deco schedule.
It doesn’t matter what your favorite method of redundancy is, just make sure you have some form of backup for your PDC. One of my instructors told me years ago that being safe isn’t hard. We all know what to do. We know the safety procedures and protocols. The hard part is having the discipline to follow those procedures on every single dive. Be disciplined. Don’t enter the water without proper redundancy.