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A Little Bit of Undersea Living History

Hydrolab: Grand Bahama Island

I thought I’d share a unique diving event that occurred almost 50 years ago. After a decade in the Royal Navy, I relocated to Grand Bahama Island and after a couple of enjoyable years at the International Underwater Explorers Society joined Perry Oceanographics and the National Oceanographic and Atmospheric Administration’s undersea research program, also headquartered on Grand Bahama.

Early morning Johnson Sea Link visit

My colleague Bob Wicklund and I spent several years living in, working from and otherwise supporting seabed living operations. The habitat “Hydrolab” was our underwater home away from home, eventually hosting almost 100 saturation dives involving wide-ranging scientific and biomedical experiments and a couple of national security studies. On one occasion we planned to set up fish collection stations “over the wall and down the ledge” at 200 fsw. To prepare for the saturation diving aspect of this work Bob and I first made several surface orientated air dives to scout locations and set up equipment. They went well and two days after the last of these bounce dives, we entered Hydrolab with a hatch/storage depth averaging 47 fsw (3.5-foot tidal range). Some 24 hours later we made our first downward excursion to the worksite. To maximize our considerable 60-minute bottom time afforded by starting out at 47 fsw we swan vertically out to the edge of the ledge maintaining storage depth rather than following the reef’s descending contour, then

Bob entering diver lockout compartment

dropped straight down to 200 fsw. Our eventual return to Hydrolab required several brief stops along the way and so became the first recorded excursion dive from saturation storage necessitating stage decompression. As unique as this excursion dive was it’s not what prompted me to write. Once back inside Hydrolab both Bob and I both excitedly blurted out that we felt so much more “awake and alert” at 200 fsw compared to our surface-orientated bounce dives. We also commented on our increased peripheral vision in contrast to tunnel vision, another associated narcotic effect of deep air bounce dives. It seemed as if we were breathing heliox rather than air, such was the reduction in nitrogen narcosis.

These effects were evident during subsequent deep air excursions, and we shared all of this with Dr. David Youngblood, Hydrolab’s illustrious medical director. David was on staff at Duke University and a colleague of Dr. Peter Bennett, a pre-eminent ultra-deep diving scientist. Peter was wholly unconvinced we were acclimatizing to high nitrogen tensions. Call it what you want, we were clearly much better off at depth following a period of intermediate air pressure saturation. Following our protestations Peter finally agreed to put our observations to the test. To do so we recruited the services of the Johnson Sea Link submersible, recently allowed to resume manned operations after its 1973 fatal entrapment off Key West. The submersible was parked adjacent to Hydrolab. Before saturating, we dove from the surface, entered the submersible’s confined diver lockout compartment, and were compressed to 200 fsw, an essential air bounce dive. Upon arrival at depth, we proceeded to undertake a battery of tests, one involving the rather delicate task of picking up and relocating small ball bearings with tweezers, a task many might struggle with in the comfort of their living room. Upon completion of testing, we decompressed to the submersible’s hatch depth, locked out and swam across to Hydrolab to begin saturation.

Decompression schedule

A couple of days later the submersible returned and we swam back to it, locked in, and were again compressed to 200 fsw, all the while it remained on the seabed adjacent to Hydrolab. The same tests were repeated. Peter’s subsequent analysis of the data failed to detect any differences in mental and cognitive function between the two 200 fsw dives. This surprised Bob and me, although not Peter! It led us to conclude that his tests weren’t specific or sensitive enough to identify what was readily apparent. Peter didn’t appreciate our discounting of his testing tools one bit but we, and others, continued to enjoy what we considered safer and considerably more productive deep air dives from saturation storage. So, a bygone era of pioneering saturation excursion procedures and scientifically unproven benefits associated with air saturation prior to downward excursion deep air dives. Sadly, Bob, my longtime friend, colleague, and pioneering underwater scientist in his own right, passed away several months ago.

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