Alert Diver is the dive industry’s leading publication. Featuring DAN’s core content of dive safety, research, education and medical information, each issue is a must-read reference, archived and shared by passionate scuba enthusiasts. In addition, Alert Diver showcases fascinating dive destinations and marine environmental topics through images from the world’s greatest underwater photographers and stories from the most experienced and eloquent dive journalists in the business.
RESEARCH, EDUCATION & MEDICINE ADVANCED DIVING bell and take over doing compressions and maintaining an open airway, while the dive team transitioned to the ROV downline. The bell, along with a support diver, would be lifted out of the water and the injured diver treated, after which the bell would be returned to the water for the remaining dive team’s decompression phase. Further protocols covered separated- and lost-diver scenarios as well as out-of-gas emergencies. When in doubt, all a diver had to do in an emergency was swim back to the bell, which would be located just above the wreck. The bell was loaded with built-in cylinders filled with the gases required for the dive. Each cylinder was equipped with multiple regulators on long hoses. Additional cylinders of deep and intermediate gas mixes were also available. ALGORITHM SELECTION Because of the very strong surface currents that can occur over the Britannic, decompression model safety factors were considered, and the best protocol was determined to be one that would promote completion of as much decompression as possible at deeper depths where the currents would not be as strong. OV_6.75x4.6525_AVS.qxp_Layout 1 9/15/16 2:10 PM Page 1 Thus we were on the hunt for bubble-based deep-stop protocols. The varying permeability model (VPM- B) and reduced gradient bubble model (RGBM) algorithms used to dictate the deep stops on previous expeditions were configured with a 10 percent increase in the “nominal” critical radii of helium and nitrogen bubbles. These models generated an initial ascent rate and a deep-stop profile fairly close to a Bühlmann model with a low gradient factor (e.g., 5 percent). Since these models were based on real bubble mechanics and not fudged to Bühlmann, we figured them to be physiologically better. As a sensibility check we compared the total run times of these profiles and found them to be fairly similar to those generated using the Drogon Dive Planner (DDPLAN) with 5/85 gradient factors, which had been used reasonably successfully on previous deep projects. With rebreather scrubber durations taken into consideration, run times were capped at 40-50 minutes. Both the Inspiration and JJ scrubbers had been shown to be good for at least five hours on deep warmwater dives, due to their efficiency in warm water in conjunction with the divers’ work rate, which was very low except during the first 30-40 minutes on the bottom. oceanviews Photo Contest sponsored by DAN ® and Nature’s Best Photography. Enter Oct. 10 - Dec. 12, 2016 © ALLISON VITSKY SALLMON Get the details and enter online: naturesbestphotography.com/oceanviews 48 | FALL 2016
THE EXPEDITION At the end of an exciting and successful expedition, on our last day of diving I joined three other divers — Italian Edoardo Pavia, American Michael C. Barnette and fellow Brit Richard Stevenson — for a tour around the wreck in a single dive. The visibility was in excess of 150 feet as we cruised the decks of the massive liner using lithium-powered Suex diver propulsion vehicles. We passed by open and covered promenade decks, under huge lifeboat davits silhouetted above us by the midday sun and over the seabed debris field to a maximum depth of almost 400 feet. We passed the three monster propellers and cruised along the stern veranda café. Each scene was truly breathtaking. Watching from the best seat in the house, Richie Kohler followed us in the Triton 3300/3 submersible alongside pilot Dmitry Tomashov, while Russian cinematographer Sergey Machilskiy caught every frame of our journey using Red Epic 5K cameras. Circumnavigating the Britannic during its centenary year surrounded by such incredible technology was without a doubt the greatest dive of my life. The dive team explores the Britannic’s propeller, helpfully lit by the expedition’s two submersibles. Tomashov’s father, Evgeny, skillfully maneuvered his unique, specially built one-man minimal-displacement submersible into various positions, lighting up scenes such as the propellers and bow. It was like we had dived into a science fiction movie, but as Kohler remarked as he climbed from the submersible hatch hours later, “Science fiction? No, I think you will find, Leigh, that dive you just made was science fact.” AD DAN Cares Together, we save lives. Whether it is assistance provided over DAN’s 24/7 diving emergency hotline, an important discovery through our continued research, or application of emergency first aid – all of these elements directly impact diver safety. With your help, we continue to invest in these initiatives because we care. Together, we make a difference. DAN.org/DANCares All contributions are tax deductible and benefit the DAN Foundation, a 501(c)(3) organization, Tax ID # 56-1696689. ALERTDIVER.COM | 49
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