The rushing water also destroyed visibility for a significant distance. Cas Dobbin and I entered the water in another column and groped through 250 feet of zero-visibility muck. When we finally emerged from the clay colored water, we could see white misty in-feeding seeps further polluting the visibility. We made our way down to 130 feet of depth and spent some time shooting equipment near the pumping station. We found a lot more interesting graffiti and even managed to identify one of the people named on the wall. His friends were assisting at the mine and told us about his prowess playing strongman on their hockey team.

Cas and I were the only ones eager to make a second dive. We worked on a video mission and searched for the best area to lay line the following day. The visibility seemed to be best on the east of our entry, as far away as possible from the in-feeding meltwater.

Our dive went well until our decompression stop when Cas tore a mouthpiece and experienced what we call a caustic cocktail. Water leaked into his rebreather and mixed with the carbon dioxide absorbent material, creating an alkaline fluid that can burn the mouth. We were in inches of visibility when he quickly switched off his loop and got on open circuit air. He coughed and I reached out to hold him. The scuba air was the same temperature as the water at 3 degrees, so he became quickly chilled. Rebreathers create an exothermic reaction that gives a diver warm moist air to breathe. Traditional scuba is like inhaling freezing air, chilling the diver more quickly. Cas handled the emergency like a really well practiced explorer and managed through the chill to complete his full decompression obligation.

After the dive, we jumped right into our medical tests and learned many more new things about decompression stress. I’ll leave the details for a future post, but suffice to say, the medical research being done here is incredibly valuable to the team and to understanding extreme dive profiles.