Lazy shot or shotline
First you have to understand the term "shot(line)" - a line held at the surface by a buoy and anchored at the bottom either by a weight (which in Britain we call a "shot") or a hook. Usually some combination of the two. This line is used to descend to the target, typically a wreck, and when there's a significant current it's necessary to hold the line all the way down to have any hope in poor visibility or high current of actually getting onto the wreck. You also ascend up the line, though when there's much current this can be hard work. The boat knows where the shotline is as it can see the buoy, which of course is fixed relative to the wreck.
A "lazy shot" is preferred when the current is bad, and is used for the ascent. It is a second line with a buoy at the top, attached at its bottom end to the main shotline by a detachable clip maybe 20-30ft down (the depth ideally determined by the expected deco profiles of the divers - they want to perform the bulk of their deco on the lazy shot).
When a lazy shot is in use, each diver carries a token unique to that diver (eg. a brass clip with a label bearing that diver's initials). On the initial descent down the main shotline each diver fastens his/her token to a loop on the main line just where the lazy shot is attached. On the ascent, also up the main shotline as it's the only one that goes to the bottom, when each diver reaches the branch where the lazy shot leaves, (s)he removes their token and continues up the lazy shotline. The last diver to reach that point will find only his token, and as well as removing it he moves onto the lazy shotline (as did everyone else before him) and before leaving that point detaches the lazy shot from the main shot. The lazy shot, which until that point has been straining in the current, now drifts with the current and hangs vertically, and everyone already on it immediately feels that it has been detached. The boat captain sees the two surface buoys start to separate, and he recovers the main shotline and follows the lazy shot until divers complete their stops and begin to emerge.
If a diver misses the main shotline on leaving the wreck and has to make a free ascent, he will deploy a DSMB which the captain will have to see and in due course follow. The other divers will be left hanging from the lazy shot still attached to the main shot and hence straining in the current - so they will know someone didn't make it. The captain will know where his divers are - on the line attached to the wreck - so normally he will leave them and follow the DSMB when it appears. Having recovered that diver he'll return to the wreck to gather up his remaining divers and recover the two shotlines still attached to each other. If at that point he discovers he is still missing one or more divers he will have to assume they also ascended free and deployed DSMBs, and will have to head down current to look for them. If there was a dogleg in the current between the surface and at depth this may not be that simple, and this is when the captain earns his wages.
OK?
First you have to understand the term "shot(line)" - a line held at the surface by a buoy and anchored at the bottom either by a weight (which in Britain we call a "shot") or a hook. Usually some combination of the two. This line is used to descend to the target, typically a wreck, and when there's a significant current it's necessary to hold the line all the way down to have any hope in poor visibility or high current of actually getting onto the wreck. You also ascend up the line, though when there's much current this can be hard work. The boat knows where the shotline is as it can see the buoy, which of course is fixed relative to the wreck.
A "lazy shot" is preferred when the current is bad, and is used for the ascent. It is a second line with a buoy at the top, attached at its bottom end to the main shotline by a detachable clip maybe 20-30ft down (the depth ideally determined by the expected deco profiles of the divers - they want to perform the bulk of their deco on the lazy shot).
When a lazy shot is in use, each diver carries a token unique to that diver (eg. a brass clip with a label bearing that diver's initials). On the initial descent down the main shotline each diver fastens his/her token to a loop on the main line just where the lazy shot is attached. On the ascent, also up the main shotline as it's the only one that goes to the bottom, when each diver reaches the branch where the lazy shot leaves, (s)he removes their token and continues up the lazy shotline. The last diver to reach that point will find only his token, and as well as removing it he moves onto the lazy shotline (as did everyone else before him) and before leaving that point detaches the lazy shot from the main shot. The lazy shot, which until that point has been straining in the current, now drifts with the current and hangs vertically, and everyone already on it immediately feels that it has been detached. The boat captain sees the two surface buoys start to separate, and he recovers the main shotline and follows the lazy shot until divers complete their stops and begin to emerge.
If a diver misses the main shotline on leaving the wreck and has to make a free ascent, he will deploy a DSMB which the captain will have to see and in due course follow. The other divers will be left hanging from the lazy shot still attached to the main shot and hence straining in the current - so they will know someone didn't make it. The captain will know where his divers are - on the line attached to the wreck - so normally he will leave them and follow the DSMB when it appears. Having recovered that diver he'll return to the wreck to gather up his remaining divers and recover the two shotlines still attached to each other. If at that point he discovers he is still missing one or more divers he will have to assume they also ascended free and deployed DSMBs, and will have to head down current to look for them. If there was a dogleg in the current between the surface and at depth this may not be that simple, and this is when the captain earns his wages.
OK?
