Cave Diving, Cave Exploration and Cave Mapping in Yucatan, Mexico
Coming ashore at Lizard Island Australia

Response to zzzzzzzz from Rebreather World

I posted a link to my article Last Dive at The Pit – Bailing Out at Depth over on Rebreatherworld.com.  One of the users, zzzzzzzz, commented on it and I thought his comment was worthwhile reposting here with my response.  The indented copy is zzzzzzzz’s comment.

Good article.

WRT keeping on schedule, OC trimix should be running a set of schedules, allowing for aborted dive, short, long and maximum schedules. This provides all the needed flexibility in an emergency. Running a single schedule is not great.

Thank you! I write the articles for people to learn from and enjoy as entertainment.

The diver had the appropriate schedules. I am not sure where you read that we didn’t have the schedules. Seems like you made a bit of an assumption to the negative. Our desire was to stay on the nominal schedule. As you might imagine, the switch to the next schedule at depth can add an unnecessary amount of decompression and gas usage. Every minute at that depth translates into about 5 minutes of deco. A switch to the next schedule brings a 30 minute penalty, something neither of us wanted to be obliged too. A close reading of the article reveals that my one minute to make the switch was built in to our nominal schedules. We left the switch on schedule.

This is to distinguish the need for time to solve problems versus making an expeditious exit. Since you experienced issues, it is astounding that the OC diver’s schedules did not allow flexibility in running schedules. Certainly, a diver targets a nominal run time for a dive, however, not carrying contingency schedules is a fundamental training issue. Recommending that someone executes faster when encountering problems is not constructive since one cannot predict how long problem solving can take, especially in an emergency.

See above.

It is also quite okay to encourage better skills integration for enhanced performance, however, not because it is an inconvenience for the OC diver.

I see his recommendation in a different light. Optimally, I would like to be able to be swimming towards the exit while making the switch. That ability would cut at least 1 minute at depth and 5 minutes off of deco saving a little less then 18cuft of gas. Additionally, it would put me closer to the exit if there were another emergency, which out of respect to Murphy isn’t completely unlikely. I can’t remember a time when only one thing went wrong when things started to go really wrong. I think Santiago’s critic is correct in that I need to work towards the ability to swim and make this switch at depth. I can do it in 100ft, why not in 280ft? That is a valid question and needs to be figured into bail out planning and needs to be trained further to develop better muscle memory. I don’t think either of my CCR instructors would have let me walk without being able to do that skill while making an exit. I shouldn’t accept it either.

On deploying and stowing regulators, especially on the fly, an added option is to set hose lengths such that the regs drape around the neck to staggered positions. This can allow maintaining several regulators in a deployed condition, allowing more time and options for stowage.

This is not a bad recommendation though going back onto the loop and doing 2.5 hours of deco this way wouldn’t have been very comfortable. Again, this is a training and equipment issue and was only identified because I took the time to actually try it out.  I wrote that I have a similar problem when I dive OC with stages.  That should have been a warning to me that it would manifest itself when I dive CCR.  It is interesting that the problems we have in the shallows are magnified under the time pressure that comes with depth.

Thanks for taking the time to read my article and provide feedback! Your ideas help me to better flush out my ideas. Keep them coming