The Devil´s Jaw by Petr Myska

410 m I haven't stopped pondering the Devil's Jaw abyss since I first dove along its sheer wall with my friend Cesar a few years ago. I urged him to tell me and later show me everything he knew about the spot and we explored it together down to about 120 feet - our scuba limits. Later on, we shared the excitement of our first Trident dives, moved by seascapes illuminated in the sub's headlights. After several missions and despite a few dreadful entanglements, the ROV let us extend our knowledge of the wall beyond the 200 feet mark. Yet, the mystery of the Jaw and its unknown depth still draws us. When I dive along its edge I often stop to sit and stare down listening only to my breathing and when I am lucky, to distant whale songs. Occasionally a school of huge Pacific crevalle jacks appears from the blackness below at a rocket speed to swirl around me, then to disappear in a flash a moment later. Every once in a while Giant mantas grace us with their company. I am familiar with the large fans of Myriopathes black corals in the upper reaches of the wall, and the fish that live around them. Thanks to the Trident we also know that from 50 meters down a thick forest of whip corals sways gently in the ever-present current. But we know little more. No one does, it seems. And so our mission to find out more continues. The most obvious question remained unanswered. "How deep is the Jaw?" Regardless of what a quick Google search might throw your way, no one has ever claimed to have measured its depth. Some sources make the mistake of conflating the information on large-scale deep-sea features, such as the Middle America Trench or the Banderas canyon with the Devil's Jaw, and claim it to be miles deep. Several local and international websites publish an interesting figure of 480 m, but I haven't been able to locate the source of this information anywhere in the popular or scientific literature and the fact that the wording of the statement is virtually identical on all websites makes me think that it was simply copied over and over again without much regard to its origin. The only peer-reviewed publications with definitive and rigorously measured depths of Banderas Bay known to me are the work of Dr. Roman Alvarez Bejar of UNAM. His studies however were conducted on a much larger scale to create a 3D model of the Banderas canyon and weren't concerned with any close-to-the-shore features, such as the Jaw. I made it a point to study them in detail and even meet Dr. Bejar during one of his visits to Puerto Vallarta. We spent hours talking about the subject and on one occasion visited Los Arcos on board his yacht. We shared a little hope that his yacht's sonar could shed some light on the topic but quickly understood that its range limited to 200 m depth will leave us in the dark. A stronger, more sophisticated equipment would be needed for that task. So I started to look for sonars. Then a very active member of the ROV forum and deep-sea researcher from Australia Jason Perry, with whom I had been consulting Trident's tether management (in other words, how not to get stuck), proposed I go medieval on the issue. "Have you considered mechanical sounding?", he asked. He suggested using a braided fishing line and a lead weight instead of a fancy (expensive) sonar. He was convinced I could get better results from this low-tech technique. A few days later we dropped a 6-pound diving weight down at the end of a 500-meter long 80-pound test braided fishing line. We hit bottom at 410 m. ... to be continued. Stay tuned. #vivanaturamexico #divePV #TridentROV#fieldnotes Banderas Scuba Republic Malecón area #banderascuba

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