At this point, you as the reader are asking “why” everyone was diving on air and not a “mix” gas. The use of mix gas and Enriched air (Eanx) or commonly known as Nitrox, as you know, 220 feet is much too deep for Nitrox, was in its infancy stages of use in the recreational world of scuba diving. Not until a few years later, did the term technical diving became the mainstay. As often cited, Michael Menduno of California started the crusade with the birth of his magazine called Aqua Corps Journal (now defunct) in 1989. Technical diving (sometimes referred to as Tec diving) is a form of scuba diving that exceeds the conventional limits – especially depth and bottom time – of recreational diving. Technical diving exposes the diver to significantly higher risks than recreational diving, including permanent illness and death, and therefore requires extensive experience, advanced training, and specialized equipment. Technical diving also often involves breathing gasses other than air or standard nitrox. The concept and term, technical diving, were both relatively recent advents, although divers have been engaging in what is now commonly referred to as technical diving for decades.
In clearer water, as McFaden had caught up with Main, Main called the dive and gave “thumbs up” twice. The dive was progressing smoothly as the two cave divers turned around and began their exit swim with Main in the lead. At several locations, the water visibility was zero and holding the guideline with one hand became necessary. Several times Main would turn his head to check on McFaden who was following close behind. This was all occurring within a couple of minutes.
As Main swam into clearer water while reaching the larger area of the sixth room, he turned around expecting for McFaden to appear at any moment. After about 30 seconds had gone by Main was concerned and was about to swim back into the poor visibility to check on McFaden. However, Main spotted Bill Gavin’s light appearing as he had just finished his dive surveying the tight siphon downstream passageway and was about to motor up into the fifth room Main swam over to Gavin and signaled that McFaden was still in the upstream tunnel. Gavin unclipped his DPV and quickly swam over to the upstream tunnel with Main closely behind. Swimming into the zero visibility, Gavin followed the guideline and soon popped into clear water and found McFaden about 100 feet off the guideline staring at a wall but otherwise appeared fine. Gavin got McFaden’s attention with an “OK” signal. They both got back onto the guideline with Gavin leading McFaden and swam through the bad visibility and into the sixth room where Main was waiting.