Pearse Resurgence Written by Richard Harris
Pearse Resurgence in New Zealand is the 8th deepest cave dive ever made, with only 41m separating the deepest 8 sites. I first dived the site in 2007 with Dave Apperley, Craig Howell and Rick Stanton. On that trip the cave was extended from 125m to 177m depth by Dave and Rick. I was hooked! I have returned on many occasions since ,and with the Wet Mules team have pushed the cave to 229m in one tunnel, and 245m in a second tunnel. At 6 degrees C, the cave is formidable and I believe there is no other site being dived at these depths at these kinds of temperatures.
Most of the equipment used by the divers is heavily modified or even home made to improve life support systems for the depths targeted. Decompression algorithms used to calculate decompression are untested at these depths, and the divers have become their own “guineapigs”, cautiously evaluating how they feel as they gradually increase the depth of their dives and adjust safety margins. It is a constant battle to minimise the exposure faced by the divers to the cold, fatigue and issues around nutrition and toileting; versus the ever-present danger of decompression sickness. The science around this is fascinating as is the physiology of breathing super dense exotic gas mixtures under such pressures. Each of the gases used (oxygen, helium and nitrogen) has its own benefits and toxicities; again, a very delicate balance.
Two pieces of essential equipment have become limiting for these dives. Scooters and lights. With the advent of the Seacraft scooters with a test depth and real world dives to 300m, we have become confident that at least piece of gear will not let us down at the limits of exploration. The ENC whilst not designed as a mapping tool, is giving us valuable information about the depth, direction and length of the cave where traditional mapping techniques are simple not possible.