AS A SENIOR IN COLLEGE, I signed up for a series of courses in Florida’s cave country to become a certified cave diver. I had been enrolled in a collegiate-level scuba program for two years and wanted to expand my dive experience to overhead environments.
When I arrived to start my training, I was assigned a buddy I had just met who already had an introductory cave-diving certification. I brought my new sidemount configuration and regulator set, all of which I had used on 10 shallow-water dives to ensure the equipment’s functionality prior to the start of class.
My equipment worked fine on the first day during the open-water skills evaluation and line-running dives. On the second day of training, I was excited for my first dive in an overhead environment at Wes Skiles Peacock Springs State Park. The dive plan was to go into Peacock 1 spring and head up the Olsen line past Pothole sink. Upon turnaround we would execute the scheduled out-of-air drill, terminate the dive, and exit the overhead following the proper air-sharing travel technique.
For this dive the instructor assigned my buddy to be dive leader and asked me to simulate an out-of-air incident at the turnaround to avoid changing diver positions. Doing this maintained the team position for the drill, as the out-of-air diver is generally in front on exit.
When diving a sidemount configuration, divers have to independently manage the volume of breathing gas in each cylinder. An uneven distribution of gas can cause divers to roll to one side and lose control of their buoyancy. Maintaining a minimum amount of breathing gas in each cylinder is essential to ensuring that you can make a successful exit from the farthest point of cave penetration.
I started the dive using my long hose connected to the cylinder on my right side and switched to the short hose on my left-side cylinder at the appropriate time in the dive profile to maintain balance. The dive continued successfully, and I switched back to my long hose as we drew closer to the planned turnaround point. Soon after transitioning to the long hose, I simultaneously felt and heard a huge bang followed by one of the few sounds that a cave diver never wants to hear: the massive gushing of bubbles.
My instructor was coming alongside me and was positioned right at the point of the blast, which caught him in the side of the head and caused him to suffer some momentary disorientation and vertigo. Anyone who has been too close to a balloon popping or an air relief valve on a compressor going off knows the feeling and can imagine it amplified underwater.
Fortunately, my university training had put me through countless out-of-air scenarios and gas-loss drills. This was the first time I had to use those skills in earnest, but the muscle memory for responding to this kind of situation was deeply ingrained regardless of my equipment configuration. Remaining calm, I determined that the leak was coming from my left side and instinctively turned off the offending valve.
I remained in position to ensure my instructor regained his equilibrium, which he quickly did. My buddy, who was wearing a thick 10 mm hood, didn’t hear the explosion of bubbles and continued kicking for about 50 feet until he checked for my light and realized I wasn’t behind him. He turned around and headed back toward us. My instructor asked if I was OK. I returned the signal and gave him the dreaded thumb, which indicates the dive is over and to head directly to the surface, whereas a turn signal to turn a dive would’ve meant that the cave penetration is over, all is well, and we could poke around and meander on the way back.
When my buddy arrived, I begrudgingly gave him the thumb as well, pointing to the tank on my left side with my middle finger to indicate it was broken. The dive plan was for me to simulate being out of air anyway, so I signaled as such to my buddy, who eagerly donated his gas because he hadn’t quite realized what was going on.
The irony of a massive equipment failure and actual low-air situation on an out-of-air training dive was not lost in the moment to any of us. We followed the proper air-sharing line travel technique and protocol for the situation as planned, and the rest of the exit was uneventful.
In the classroom we disassembled my equipment and determined that a high-pressure seat failure had caused the diaphragm to bleed high-pressure gas into the environmental seal, and the bang we heard was the silicone environmental seal extruding from the top of the first stage. The high-pressure seat is the valve mechanism that opens and closes to maintain intermediate pressure. If the seat has a defect, then the valve can’t close properly and the high-pressure gas will leak past the seat and cause a buildup in intermediate pressure. Typically the second stage would relieve this pressure through a freeflow, but in this case the diaphragm itself let go.
A failure like this occurs from improper assembly at the factory or manufacturing defects in the components themselves. Improper assembly would typically show upon first testing, and the manufacturing defects typically only present as intermediate-pressure creep or a freeflowing second stage. Regardless of which aspect was the culprit, an equipment failure such as this one is rare.
Proper out-of-air training and practice are important so a situation like this will not be the first time a diver is exposed to it. Had I not had the level of skill repetition positively enforced by my collegiate instructors, Larry Brown and Matthew Rever, this event could have easily spooked me out of cave diving.
Similar near-misses have caused divers of all levels to prematurely leave the sport. I encourage anyone who feels that they don’t have the skills or confidence to safely experience a real out-of-air situation to seek additional training to help build those skills and the confidence to execute them.
If you do possess adequate skills and the self-assurance to perform them under duress in an unexpected event, make sure you practice them every year at minimum to ensure that you can appropriately use your training if the need arises. AD
© Alert Diver - Q2 2023