The Abyss in Nahoch Nachich - December 2004
My final dive of the trip was the biggest cave dive that I have done to date. Here's the gear preparation. Our equipment list consisted of our double 80 c.f. mounted on our backs with two 80 c.f. stage bottles attached on our left chest and hip D-rings and a Silent Submersion UV-26 DPV shown below. Our dive was to the Abyss in Nahoch Nachich.
Sergio Preparing His Gear for the Abyss. My Gear is in the Foreground
From the Nahoch main entrance, we begin breathing off of the top stage across our chest. While on the scooter your air consumption is quite low though the ride is far from stress free. The cave is whipping by at what seems like an incredible rate ( ~ 2 mph). It takes a constant vigilance to steer through the passage and maintain visual contact with the guideline at all times. One of the greatest dangers with a scooter is inadvertently making a visual jump to the wrong line. While swimming, you can easily pause and verify the guideline configuration. If you get concentrated on your gauges, steering or collision avoidance, jumping to the wrong line on the scooter is unfortunately all too easy to do.
The first section of upstream Nahoch is fairly easy to navigate with a scooter since the tunnel is wide and floor to ceiling height is greater than 10 feet. The first stage took us to about 6,000 feet penetration where we dropped the tank and tied it onto the guideline. Switching to the second stage, we proceeded toward the Abyss. Now the scooter speed is significantly increased without the presence of the first stage. At this point, the tunnel has also closed in on us and negotiating the cave takes quite a bit more attention.
After about another 30 minutes of transit time, we came to a tunnel to the left where we dropped the scooters. The cave has now gotten too tight to use them. We are still breathing from the second stage when we make the jump. Floor to ceiling height is less than 5 feet with the horizontal extent ranging from 5-10 feet.
At about 20 minutes from the scooters, Sergio signals to drop the last stage. He made a final jump and we were in a very tight tunnel, one where the restrictions are small enough to have to scrape through. We traveled for about 5 minutes and suddenly, the tunnel opens up to reveal a dome above us more than 100 feet in diameter. Our depth is just 20 feet. This is the Abyss...
Kicking up over a small rise ahead of us, the true nature of the Abyss is revealed. Stretching down before us is a plunging hole of 240 feet depth that narrows to a small point looking something like a funnel at a 30 degree angle from the vertical. The water is so clear that you can see minute detail in the rocks at the bottom of the Abyss. It was quite an impressive sight. We are now at 110 minutes and 10,000 feet from our starting point as we plunged over the edge.
The plan was to make our maximum depth and then spend the minimum amount of time doing deco in the Abyss. We did not need to complete the deco since our final 20 foot deco "stop" would be performed on the trip back to our exit - a 75 minute journey. At 205 feet, the Abyss narrows so that divers have to pass single file. I stopped there and turned to get to a shallower depth while Sergio continued on and his light disappeared beneath a ledge. In my nitrogen soaked mind, he was gone an eternity. It turned out to be less than a minute. By the time he returned, I was at 190 feet with a slightly clearer mind.
Since the Abyss narrows to a point, there is nothing to explore at the very bottom. So, we did a leisurely ascent while examining the walls of the ever widening tunnel. Decompression was slightly makeshift since the computers we carried try and force the diver as high as possible in the water column. As I am doing my 40 foot stop, both computers are screaming that I should be at 10 feet. Essentially, the makeshift portion of the deco is that you have to guess when to leave the 30 foot stop with deco time still piling up on your computer because you are not at 10 feet. We spent about 15 minutes on our ascent.
The trip back should have taken about 75 minutes because we would be scootering with the current. Whenever we reached one of our dropped stages, we stopped and switched to breathing off of that tank. The return was trouble free. However, at about 2,000 feet from the entrance, my scooter starts to slow down considerably. The last 1,000 feet of the trip was made with the nose of Sergio's scooter against the bottom of my tanks pushing me along. Otherwise, I would've had to swim the final distance dragging the 100 lb. scooter out.
What a great dive!