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Maybe we U.S. (North) East Coast wreck divers should explain ourselves to the British wreck divers. As in British wreck diving, decompression is routine, and visibility is frequently as low as 6' (2m). Temperatures are similar. The anchor line is generally used as the descent line. A few captains drop a Danforth anchor in the sand, pay out line, and drop a seperate descent line. But currents can run 4 knots, wind and currents can shift while some divers are down. So the common procedure is to grapple the wreck directly, and the first diver down ties in the otherwise very insecure grapple anchor. The last diver frees it. One's chances of not finding the anchor line/ascent line, within the limits of one's air supply (including air for the planned decompression stops), are significant. This has happened to me twice (on the same day), due to an inadequately tied in anchor. I have never yet been unable to find the line due to navigation error, but I have come close (once I found it during my ascent). Live boat diving is not practiced. Everyone goes in at their own pace, is responsible for their own profiles, their own surface interval, etc. There are no formal "waves" of divers. Different divers plan very different bottom times, depending on equipment, experience, and risk tolerance. The commonly practised emergency procedure for not finding the anchor line is to pass a sisal line through a piece of the wreckage, then attach a lift bag, and partially inflate it. Then you let lift bag take off to the surface. Once the line is fully extended, you tie it off at the bottom, and use this as your ascent line. After the hangs, you ascend to the surface. If possible you unclip the bag and swim back to the boat. If current/wind/waves make this impossible, then someone swims a line out to you. The line itself is lost. Sisal is both strong against the abrasion against the wreckage while being let out, and biodegradable. This way the wreck does not become littered with tangly nylon line, menacing future divers. What is in practice done in Britain? How are conditions different, and how do they affect the procedures? The BSAC manuals have some details, but they do not seem to be quite complete. I do not quite understand how the "breakers" work - what size/strength line is used as the weak "breaker"? Safe Diving Wrolf P.S. I am British, but I live and dive in New York.
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