So after twenty-four hours of travel and very little sleep on route, Craig, John, and I set up camp. We join Dave and Rick to catch up on their progress. Dave has spent the last couple of days setting up the camp and preparing the habitat while Rick has been caving on the well-known Nettlebed Cave through-trip with some locals. John feels fresher than we do, so decides on a dive before dinner to stage two tanks for the team.

A recent flu had caused John to delay his arrival in the Pearse, but he feels completely recovered now. He dons two 12-litre side-mounts and follows the line into the Nightmare Crescent and down into the shaft to stage the two tanks at 36m. He feels warm and comfortable in the cave, and is starting to admire the beauty of the site, when at 23m he suddenly starts to feel unwell….

Back on the surface, Dave and then Rick descend into the cave on their dives. The absent stage bottle is probably noted, but as the planned dives were not deep or long, little concern is raised. Craig and I are still settling in to camp, and only start to become concerned about 90 minutes after John commenced his dive.

After about twenty minutes, another glow appeared. I flashed my light but the glow faded away. I thought about getting dressed so I could dive down if the light reappeared. I was still very off-balance and had trouble thinking clearly. If I tried to dive, I didn’t know if I would stay conscious, or if I could come back to the chamber. Then the whole rift and pool lit up. It had to be Dave with his bloody great camera light.

Then my instinct just said go for it! I got my gear on as fast as I could and dropped down the line with my vision narrowing, one hand sliding down the wall by the line to keep balance. I could see Dave’s helmet lights below, and then the outline of his yellow rebreather case. I couldn’t tell if he saw me or not, even after I signalled with a loose torch. I was so dizzy. I didn’t want to leave the wall and swim to him, but after a minute he came up and we surfaced in the chamber together.

The second dive had only been a couple of minutes long but I felt dreadful again. Taking the reg out of my mouth I said “Dave, I messed up. I’m in big trouble, I feel really dizzy….”

The next day Craig and I (with growing respect for the cave!) both have uneventful shakedown dives to the bottom of the main shaft at 105m. The experience of following Dave down with the shaft illuminated by his SS HMI light is one I will never forget! Dave and Rick continue pushing the cave, and over the next few days we are passing Dave’s previous exploration to the back of the Big Room and beyond. This point has defied further exploration for the last few trips. The cave is hard on equipment and diver alike, and to finally pass this point is a huge relief, especially for Dave who has battled the cave on so many occasions. It is soon clear that two leads extend from the far side of the Big Room. The lower, larger one (now called the Brooklyn Exit) is dark and cavernous, and drops away at a steep angle before starting to level off into the “M40.” It finally ends at nearly 160m with another abyssal shaft dropping down into the blackness! Rick and Dave alternately push the deeper section of the cave laying 6mm line from an improvised reel, the dives leapfrogging to 157m, 160m, then finally Rick’s astonishing, record-breaking dive to 177m. Harry and Craig happily fall into a supporting role, and make their own exploration dives to 137m.

Rick’s final dive to 177m is performed using his side-mount rebreather, and has a total duration of 6 1/2 hours. The final two hours are spent in the relative comfort of the habitat breathing oxygen at 6m, listening to Craig’s MP3 player, and eating chocolate. He surfaces at 9 p.m. to a cold, rainy night and his anxiously waiting buddies! He has discovered that the deepest section of the cave curves back underneath itself then again pushes onward, deeper and longer. The Pearse Resurgence is becoming a serious obstacle to exploration!

Further exploration of horizontal tunnels at depths over 160m will require a rethink of diving techniques. The team is discussing the possibility of deeper habitats and other high-tech approaches to unravel the deep mysteries of the mighty Pearse Resurgence! Heaven forbid the cave goes deeper! Or what if it headed up from 180m into dry passage?! Talk about remote dry caving! The logistics seem insurmountable. Stay tuned!

Analysis of John’s incident

The sudden and near fatal onset of vertigo and perceptual narrowing during the descent phase of John’s dive is extremely interesting from a diving medicine perspective. Vertigo describes the sensation whereby the victim feels as if the surrounding environment takes on a spinning motion. It is completely disabling as all normal visual reference points are lost. Up and down, left and right become indistinguishable. Severe nausea and often vomiting follow.

In the context of diving, there are several well recognised causes of vertigo, some of which can be immediately discounted. Inner Ear Decompression Illness (IEDCI) is now well described in both air and mixed gas divers. However, as the problem occurred on the initial descent, that is not the cause here. Inner Ear Barotrauma (IEBT) which can occur by similar mechanisms to middle ear barotraumas, i.e. failure to adequately equalise the pressure changes occurring within the middle ear. John did not describe any difficulty equalizing at any time, nor did he forcefully equalise during the descent. Alternobaric vertigo is a possible explanation. In this problem, one middle ear space equalizing at a different rate to the other can indirectly cause a pressure difference between the two inner ears, producing transient vertigo. A recent upper respiratory infection or viral illness could perhaps pre-dispose to this condition. Caloric vertigo (the sudden filling of one external ear canal with cold water causing dizziness) is also a possibility in the icy waters of the Pearse.

John’s history of a recent illness, and the fact that he continued to feel unwell for some weeks after the event, suggests that this was a contributing factor. A viral infection of the balance mechanism of the inner ear in combination perhaps with alternobaric or caloric stimuli is the most likely cause in the author’s opinion. The perceptual narrowing or feeling of impending unconsciousness is well described in the cave diving fraternity, when divers feel faced with their probable death.