Cave Diving, Cave Exploration and Cave Mapping in Yucatan, Mexico
Chico at Cian Ka'an Park Mexico

8000 Feet, One Spool and One Total Loop Failure

A traverse from Naharon to Mayan Blue on rebreathers.

This past week has been very busy for Patrick and me.  With the arrival of “Slow Season” here in Playa Del Carmen, we have found more time and more opportunities to get ourselves into some serious dives.  We have made two trips to The Pit and one trip to Sistema Naranjal with our Megalodons.  Luckily, the dives at The Pit were relatively excitement free, other then Patrick reaching the restriction at Jill’s Chamber at 105 meters.  However, the dive at Naranjal was anything but boring.

Patrick had finished up a full cave class at Mayan Blue on Sunday.  Unfortunately, the student didn’t complete the A Tunnel / Death Arrow circuit, so we had to retrieve the remaining gear, one spool.  We decided the only reasonable way to do the clean up dive was to traverse from Cenote Cristal (Cenote Naharon) down to the Death Arrow jump, pick up the spool, and swim back.  The swim from Naharon to Mayan Blue typically takes about 2 hours.  We decided to cut the swim a little short by only going to the end of the Death Arrow passage.

When we were planning our bailout gas, I was worried about having enough.  I hadn’t swum this distance and I wasn’t sure of the depths.  Patrick and I agreed to take 2 Aluminum 80’s each.  We ran some calculations and it was enough to get us out if we needed it.  Patrick’s calculations showed that two 80’s would last him 4 hours at this depth.  My SAC is higher, so I didn’t have same cushion.

When it came time to decide on our gas mixes, I asked Patrick what he was taking?  He told me Air.  And then we got into a discussion about bailout.  He very sternly explained to me that the choice of bailout gas didn’t really matter.  He didn’t believe he would ever have to bailout.  However, if he did he would only be punished with deco time.  He explained that he follows a checklist and is meticulous about assembling his unit.  I told him I was going to take 32% regardless of his feelings on the topic and I was going to drop a tank of O2 in the cavern for good measure.  You really never know when something unexpected is going to happen.  Isn’t that the definition of unexpected?   We agreed, or I decided in my head, I can’t remember, that if someone bailed out, they would get the 32% and the Air would be the gas of last resort.  At this point, Patrick’s attitude really concerned me and I decided that I was going to have a sit down with him, but I was going to wait until after our dive, as to not mess with his head.

Wednesday arrived and we got on our way.  The dive was going according to plan.  We passed the restrictions heading for Mayan Blue.  At the T, I wanted to “drop” a cookie.  As I got my markers out of my pocket, I dropped my safety spool. I reached for the safety and lost control of my buoyancy and started to fall.  I reached for the inflator, but no luck!  I ended up rolling down the windows saving myself from crashing into the mud, but creating some silting.  I could hear Patrick laughing as he watched this comedy of errors.  I finally got my act together, marked the T and proceeded.  I am sure it looked hysterical, you know how things happen in super slow motion, I know I was laughing about it.

We arrived at the spool at 80 minutes.  He retrieved the spool and we rested briefly.  When we finally got going on the return trip I was in the lead.  We were singing into the DSVs and just enjoying the dive.  After about 10 minutes we settled into a decent rhythm and pace.

At about 20 minutes, I saw a quick flash of the light head of me.  I instinctively turned and started to swim to Patrick.  We were about 50feet apart.  It took me a second to process the situation.  What I saw was one of the breathing hoses from the KISS Classic just floating in the water and I saw Patrick deploying a bailout reg.  My first thought was, ‘Oh shit, what do I do?  My bailout regulators are really secured and are not quickly accessible.’  Before I was close enough to help, he got his regulator out.  I arrived and assessed the situation.  The exhale breathing hose had disconnected from the canister.  At Patrick’s request, I reattached the hose.  We thumbed the dive, changed positions and started swimming.  This is when my heart rate finally picked up and I became aware of the gravity of the situation.  This was a real live catastrophic loop failure way back in a cave.  This is the exact type of unexpected situation we train and prepare for.  I knew we had enough gas, but I still got hit with some adrenalin.  I had to stop and think about my breathing and heart rate for a second.  My heart rate really isn’t under my control sometimes.  The base of the brain just reacts.

As we swam, I stayed near to Patrick in case something else went wrong.  I checked my computer and marked the time.  We had 60 minutes of swimming up stream to exit the cave.  Patrick cleaned up his hose routing and attempted to go back on the loop.  As I watched him attempt this, I just kept thinking, “You can’t recover a KISS from a total flood.  Don’t try.”  He found out in short order it was a done deal.  Then I offered him my 32%.  He waved it off, and he started to play with his X1.  Patrick later told me he thought he would be fine on air.  However, a couple of minutes later when we reached the T, he realized he was running out of no stop time and asked me for some 32%.

He asked at the worst time for me.  I was about to pick up my cookie and had too many things going on at once.  I struggled with my tank for a minute and finally told him to start swimming.  It would be easier to make the switch underway instead of hovering.  At this point I made a mistake, I think I was a bit overloaded and my brain was fried.  Instead of doing one thing at a time, I had the tank neck out of the bungee in the left hand.  I reached down to get the cookie with my right.  Now I was swimming with both hands full trying to get my tank completely off.  Ug! What a nightmare!

I finally stopped and stowed the cookie.  Then I passed the tank to Patrick.  He reached down to pull the regulator off the tank and the mouth piece came off!  The irony is that Patrick recently told me it was stupid to put the bungee necklace under the same zip tie as the mouth piece and that the mouth piece would come off at the worst time.  I defended my choice and didn’t change my configuration.  The bungee was wrapped around the tank neck and under the single zip tie.  When he showed me the regulator without the mouth piece, I could hear his voice in my head and I laughed.  I have since changed my configuration for CCR diving.  I removed my 120 degree swivel and the necklace on the bailout regulators.  I want them to be as accessible as possible.  Now, I believe that I will need them at the worst possible time.  He replaced the mouth piece and started to enjoy the joy that is 32% EAN.

Patrick swam off and I struggled with his tank.  This dive taught me my sidemount bungees are too short to be useful in an emergency.  As I struggled with the tank, I swam into the ceiling with my rebreather.  It got a little hung up so I jerked my head down.  I immediately realized my head was way heavy and I was heading for the floor!   A huge rock had broken loose and was on its way to pinning me.  I rolled to the right and the rock fell off my head before I hit the ground.

Again, I laughed.  I couldn’t believe how many things had happened to us on a single dive.  We have been diving for seven months together and all of those dives had been incident free.  A series of walks in the park, including cave dives to 300ffw.  The type of diving that breeds complacency.

I caught up to Patrick and we continued to exit.  We decided to pull our gear.  As I pulled my spool from the jump between Southern Sacbe and Southwestern Sacbe, I created a nasty knot around the main guideline.  I ended up cutting the spool free from the guideline.  It was the last in a row of incidents.  We exited safely with a total run time of 180 minutes.  I estimate the total distance at around 8000 feet.

Patrick and I agreed that we handled all of the situations acceptably.  We did a serious review of the dive and have both made changes to our rigs and attitudes.  As I mentioned, I changed my regulators and I lengthened the sidemount bungee.  Patrick also made some changes to his regulators to ensure they are accessible.  We adjusted our bailout gas attitudes.  And we agreed to take better care to avoid team separation.

Once the stress started to pile on, it made simple tasks like a tank swap more difficult.  A task he and I normally can handle in a minute or less took a couple of minutes.  My overall awareness decreased and we got a good distance apart more then once after the main failure.

I feel it was an excellent dive!  We both returned and no one was hurt.  We tested our abilities as a team, and as individuals in a stressful situation.  We both stayed calm and controlled our breathing.  We reacted instinctively and completed the tasks at hand.  We realized our performance wasn’t perfect but it was acceptable. The whole dive confirmed to me the following idea.  Bailout is for unexpected situations and it does matter.  No matter how bullet proof you might think you are or your procedures, unexpected shit happens and it will happen at the worst time.  And these situations never happen alone, they are always compounded by other events.

Patrick used just over 2000PSI from one Aluminum 80 to exit from 60 minutes into the cave.  I hope you learn a little from this, I know I have learned a lot.

As always, your comments and criticisms are welcome here.  If you want to know more about the incident, leave a comment and one of us will respond.


1 Hans { 07.29.08 at 12:03 pm }

CaverKevin on The Deco Stop asked, “Can you share more detail about how and why the hose became detached?”

My answer is:
To be honest, we are not sure how it happened. Our theory is:

Patrick assembled the unit and checked the hand tight fitting before he entered the water. My experience is that he is very very careful about assembling his rig. So I believe he checked and double checked.

We think he may have left a twist in the hose that put some tension in the system. Tension that would unwind the bayonet connector if allowed too.

During the dive he was developing a lot of condensation in the loop and it was gargling. So every so often he would remove the dsv, hold it above his head, lean to the right and shake it a bit to clear the water. The last time he performed this procedure, he shook it particularly hard. This is when the hose detached. Holding the loop at this angle could remove the locking tension from the bayonet and allow it to unwind.

We had passed a couple of restrictions and made some contact with the cave. That may have been a contributing factor.

We really don’t know what happened. That is an educated guess.

However, I have an alternate theory. God reached down from heaven and detached the hose to teach us a lesson. Just another act of God, like a tree falling on my car.

I know that is a long shot, but we really never came to a solid conclusion. An inspection of the unit never revealed any problems.

2 J. Evans { 07.29.08 at 12:17 pm }

What makes you both competent divers are the resulting tactics
used in an accident prone situation-! One or both of you may have perished had you not stopped & thought about what your next moves will be-! You don’t learn this in class, you learn it by experience-!
But what do I know……I’m only a novice cave diver-! Who has been here & have done what you guys have just been thru. Perhaps not in the same system or breathing mediums, but never-the-less, a panic situation turned into a strained but successful dive-! Your next dive will be even be better & more enjoyable for both of you. Very smart & nicely done.


3 Doppler { 07.29.08 at 12:51 pm }

Good write-up on what seems to have been an excellent dive. Glad the two of you were fine. I am interested to hear more details concerning what “adjustments” you have since made to your bailout gas strategy.

All the best

4 IG Saturation { 07.29.08 at 1:11 pm }

Glad it went well and thanks for sharing. A lesson for everyone as more RB divers make it to caves.

5 Andy { 07.29.08 at 1:14 pm }

Glad you both made it out o.k.
You have reaffirmed my belief in “more than adequate” bailout


6 Hans { 07.29.08 at 2:08 pm }


I think the first change was that we were reminded we may really need to bailout and the bailout gas we carry can have a serious impact on the overall dive. Andrew told me when I was training on my Meg that the very high reliability of the unit may actually be a problem. He explained that after some amount of time you will start to believe the unit is perfect and won’t fail. It is an insidious kind of confidence creep. I think a failure every once in a while in a real world situation, is beneficial. If I am teachable, I can reset that confidence creep. But I digress.

We reaffirmed the idea that having the right gas mix and having the regulators optimized for that task is critical. We agreed to be more conscious about our mixes and having the right mix for the dive. In 50ffw of water, this isn’t that critical, it is more of an annoyance. But two days later we were at The Pit and Patrick was making a 350ffw cave dive. The mixes are more critical. The stakes are much higher. That decision lead to a bunch of new blending just for Saturday’s dive and a commitment to make the appropriate investment and not be lazy.

Additionally, we had been debating whether or not to switch to team bailout. We both were adamant believers in individual bailout, however, after months of diving as a team and building confidence in each other and our equipment we started to believe team bailout was a good idea. The dives we’re doing are starting to require substantial numbers of cylinders and the logistics are becoming a pain. Team bailout seemed like a good solution. I think we were both squarely pushed back into the individual bailout camp. Rebreathers fail in unexpected ways and there is no reason to run short on bailout. Who wants to make a choice about who lives and who dies? What a horror show. We joke about the dead man’s hand shake, but I loath to ever be in that situation.

The next big change for us, as a team, was to agree to optimize our regulators for the task at hand. We had been sharing our regulators between our side mount rigs, which I use for +75% of my diving, and our rebreathers. Neither of us wants to be taking them apart and reassembling them a couple of times a week, yuck. It is annoying and adds lots of room for a failure. However, what I learned was that Patrick can’t read my mind and didn’t realize I wrapped the necklace around the tank neck. He pulled the regulator away and pulled the mouth piece off. It wasn’t an emergency, but if I needed to deploy that regulator when he first bailed, we would have been in trouble. So, when I am on the rebreather I remove the necklace, remove the 120degree swivel and make sure the regulator is in a place I can deploy it quickly. He made similar changes that included dedicated regulators to the bailout task. You never know who will need the gas you are carrying or what the situation might be like.

I think it is worthwhile to reaffirm the fact that neither Patrick nor I ever suggested carrying less then the four 80’s plus a 40 of Oxygen at 20 feet. Out of the 320cuft of gas we had with us in the cave, we used a little more then 53cuft for the whole incident. I think our gas planning was sufficiently conservative. The only debate prior to the dive was over the choice of bailout gas. And the fact of the mater is that the team approach worked, we had enough of the right type of gas to exit with out any deco obligation. We never worried for a moment about the gas volume.

I hope that answers your question.

7 john routley { 07.29.08 at 2:15 pm }

well done guys, tricky situation to be in, but handled well, and good lessons learned,
I’m not happy with bayonet loop fittings with out them being secured.
we have some here in the shop sent to us as proto types a long time back. and they can disconnect with only a 3rd of a turn…scarry.
kind regards john routley

8 Mark Chase { 07.29.08 at 3:53 pm }

Is that Patric the ex underling to Matt Mexico?

If so id love to have been a fly on the wall during Matts debreif on the dive M8 😀

Great write up, thanks for posting the link on RBW .

9 John K { 07.30.08 at 11:29 am }

Hi Hans

I always enjoy your “how do we improve” reviews. Having dove with you before I know how seriously and professionally you had the pre and post dive planning and review. Thanks for sharing the learning experience. I have a Kiss Classic that was pre-bayonet connection so I have the old hose clamp attachements. Maybe I will not be looking to make this particular upgrade in the future.


10 Marco { 08.03.08 at 10:22 pm }

Hi Hans, the way you wrote this particular dive made me go straight into it. Good to hear you guys are ok.

11 Hans { 08.03.08 at 11:04 pm }


Thanks for taking the time to read it and chiming in! The dive was as entertaining for me as it has turned out to be for my readers. That is awesome. I am glad all turned out well also. Keep on reading and commenting!


12 Polly { 08.18.08 at 1:24 pm }

Thanks for posting your experience. This story is a reminder to all (CCR, SCR, OC) the importance of not falling victim to complacency. Also that it is important to practice emergency procedures on a regular basis so you are able to perform them (as you guys did) 1000s of feet back with the proverbial poop hits the fan.

13 Hans { 08.18.08 at 7:51 pm }

Polly, I can’t agree with you more. The reason I posted the story was so it could serve as a warning that these things really do happen, no matter how prepared you might be. My instructors always tell me that the only skills you will keep when things get really stressful, are the ones you over practiced and know instinctively.

Thanks for the comment! Keep on reading.