The weather was so poor when we did our Deep Specialty in December that we couldn’t actually get to the 40m depth. We did the two deep dives to 22m and 26m instead. Anything below 18m is considered a deep dive, so we were still able to get certified. Today, Neil took all of us DMTs on a 40m deep dive at Chumpon Pinnacles. This is an essential part of the PADI Divemaster Training. I was excited to finally experience this depth! It is pretty much the same as any other dive with a few considerations. We will be under 5 bars of pressure at 40m, meaning we will breathe our air 5 times as fast and absorb a lot of Nitrogen. This means we have relatively short no-decompression times. We also need to carry torches due to low light and low visibility. In addition we do not want to be underweighted so we usually carry a little bit of extra weight. We check our equipment just as thoroughly, but there is an additional care factor when deep diving. My buddy was Paul. He’s a great diver, very professional and thorough. After our comprehensive buddy check, we did a bubble check at the surface in the water. We check for bubble leaks on each others equipment. Mainly the first stage and SPG hose. If there are small bubbles there is no problem, but anything more serious and we would need to change equipment for this dive.
At the buoy line, Neil signaled for us to descend. Emma and Nathan were at the front, Paul and I in the middle and Bobby and Ryan at the back. As our objective was to dive deep, we had to descend relatively fast, right past all the fun divers into the deep blue. We did a free descent down and initially you could not see the bottom. When I felt that I was already quite deep, I checked my dive computer to see that we had just reached 20m depth. I signal OK to Paul. OK back. We were only half way down, 20 more meters to go.
We descend further and at around 30m hit a thermocline. The visibility went from excellent to poor in a split second. We made sure we stayed very close in order to not lose each other. Sometimes I could just make out a shadow in front of me and I knew that’s either Emma or Nathan. Gradually we were approaching the 40m max depth of our dive. It is hard to describe what it feels like. We were diving on 27% Nitrox, which may have reduced the effects of Nitrogen narcosis slightly, although this isn’t scientifically proven. I did get a little bit light headed and when I signaled to Paul, he was in a similar state with a silly grin hidden beneath his mask and regulator. The thought that there is 40m of water above you at the time is less scary once you are down there. You also don’t feel the pressure as such. I felt that breathing the air was a little strange. It almost felt as if it was thick. The density of the air we breathe at that depth is 5 times as high as at the surface, so if my lung holds 5 liters at the surface, I was breathing 25 liters of air in one breath compressed to the 5 liter volume of my lungs. We also use unbalanced regulators, meaning it does not compensate for ambient pressure and it does become harder to breathe at depth. A combination of these things make for a unique diving experience. In addition it is the knowledge that you need to be absolutely 100% focused. If anything goes wrong at this depth, it is a long way up to the surface. We check our air much more frequently for example.
On the sand at about 39m we kneel down and I get swept into a sea urchin. It was the only one I could see anywhere! They hurt and this one stung me right in the knee cap! Keep calm. Then we realise that we have lost our last buddy team. Neil began to bang on this tank and we could hear tank banging coming back. It’s so difficult to determine sound direction under water, so we were unable to relocate them. We therefore kept our bottom time short and began swimming up to the dive site, gradually decreasing our depth. It is very important that we make a very slow ascent to the surface to give our body’s slower compartments time to release the Nitrogen at shallower depths. We held on to the buoy line during our safety stop to ensure we remain no shallower than 5 meters for at least 3 minutes. Our third buddy team ascended because Ryan was uncomfortable and felt the effects of Nitrogen narcosis. They did the absolutely right thing and slowly ascended to the surface. Because we were a group of DMTs with our own surface markers, this was no issue. They are more than qualified to ascend as a buddy team. The visibility made it impossible for them to clearly signal Neil under water. A very cool experience, can’t wait for my next deep dive! Thinking about leading fun divers as a Divemaster on a 30m or even 40m dive is still a scary thought…