CT-Rich
Contributor
Unfortunately, or fortunately, no one reports on dive accidents that you walk away from. Non-fatal accidents requiring either medical treatment or Coast Guard assistance might be getting reported, but even then, the data will be spotty.I agree that we can not assume there is any relationship between a diver found dead on the bottom and the failure to drop ballast. I also think we should pretty much assume that most significant cardiac events which occur on the bottom are not survivable, but that does not mean that ditching lead is not critical in some situations.
In order to understand the importance of dropping lead, it would seem necessary to also look very carefully at the NON-fatal accidents and incidents. How many people were saved, or avoided sinking further into the incident pit by dropping ballast? That is the type of statistic that would seem most relevant to determine he efficacy and safety of dropping lead.
I'm not a statistician, but it seems to me that in order to understand the importance (and negatives) of dropping lead at the surface or at depth, you would want to try to look at the number of people who died from embolisms (or DCI) that dropped lead at depth (and maybe assume a larger percentage of those cases were caused by dropping lead) and compare that to the number of people who have "walked away" from the situation with zero (or minimal) injuries. For example, if 10% of the people die and 90% of them walk away, then we might be more comfortable with the concept of dropping lead at depth.
Also, the discussion of dropping lead (at depth) tends to be very polarizing and always seems to be excessively biased from the PERSONAL perspective of the diver. More specifically, the significance (or danger) of dropping lead in a warm water situation (with minimal exposure protection) is probably small because we are talking about a "modest" amount of lead (maybe 3 to 10 lbs or so). I typically dive with zero to 6-8 lbs of lead on a belt - so dropping the belt would be a no brainer for me if it was a no-deco dive and I thought it was possibly necessary.
Conversely, if you are wearing a 25-lb weight belt and drop the entire amount, the resulting buoyancy change can most definitely be significant and dangerous. In any regard, we are constantly hearing the overly simplistic, comment that ditching lead at depth is going to send you rocketing to the surface. NOT a valid assumption in all situations.
I personally feel that for recreational diving, having 6 or 8 lbs of ditchable lead is much safer than having all lead integrated and unable to be jettisoned on the bottom.
If you want to find out the efficacy of dropping weights, you might want to talk with a charter boat captain. One that has been around ten or more years. If a charter carries 10 divers for 2 dives five days a week in ten years he woul have over seen 50,000 dives. He'd have seen pretty much every type of screw up imaginable and would good idea how often divers walk away from ditching lead at depth. It's anecdotal evidence, but statistics on dive accidents is less than perfect anyway. Commercial and military divers might have data, but that is an entirely different beast.
An unconscious diver shooting to the surface will probably only make the body recovery easier. The divers that are most likely to need to dump weights at depth are going to be newer divers, who tend to be over weighted anyway.
The dumping lead at depth discussion always reminds me of the seatbelt argument that focuses on the remote possibility of the car landing water and sinking while you are belted in...
Since we're on the subject of dead divers, what percentage of dead divers are recovered with gas still on their back?