When a death occurs during an organised recreational activity, the certification agency's insurers will usually send an investigator to look into possible liability issues.
In most cases the body will have been recovered and resuscitation attempted, and in this process equipment is usually removed and may be damaged or lost, or the evidence compromised by handling.
The ability to provide documentary evidence showing that correct procedure was followed can simplify the investigation and may lead to more accurate and reliable findings.
These generally log a dive profile by recording depth and time at regular intervals, and this data can usually be downloaded or inspected on the instrument.
[12] to be expanded[1]: Ch11 There will generally be regulatory requirements regarding both the performance and record keeping for a professional dive, and these may vary in detail depending on the jurisdiction.
Where diving falls under occupational health and safety legislation any accident occurring at work may be investigated by the responsible OHS organisation, and if criminal activity is suspected, also by the police.
The data logged by the computer can be useful in determining the details of the dive profile and interpreting the sequence of events, particularly where there is no communications recording available.
It is standard procedure for many (possibly most) contractors to record the voice communications of the dive and retain them for at least 24 hours, or longer in the case of an incident.
After cleaning, disinfecting and reassembly, the unit is test dived, in case there is some subtle problem that can be detected by an expert user, such as buoyancy, weight distribution and performance in various orientations.
[1]: Ch4 Physiological triggering events that may lead to a diving accident, but are not generally the direct cause of death include nitrogen narcosis, dehydration, exhaustion, hypothermia, excessive work of breathing, motion sickness and the effects of alcohol and recreational drugs.
A properly equipped diver following recommended practices, diving in an environment compatible with their competence and in good health should not drown.
A study by William P. Morgan indicates that over half of all divers in the survey had experienced panic underwater at some time during their diving career.
Loss of buoyancy is less of a problem to surface supplied divers as they have a lifeline and do not easily run out of gas, but an uncontrolled ascent can be dangerous even when there is technically no decompression obligation.
Carbon monoxide produced by overheating of the compressor, or by contamination of the intake air by internal combustion engine exhaust gas is a well known risk, and can be mitigated by using hopcalite catalyst in the high pressure filter.
[30][31] Contamination by carbon dioxide is unusual in open circuit breathing apparatus, as natural air usually has a low enough content not to be a problem at the ambient pressures of most dives.
Scrubber breakthrough can occur for a variety of reasons, most of them connected to user error, but some more likely due to design details of the specific unit.
[32] Both oxygen toxicity and hypoxia may render the diver unconscious without warning, and decompression sickness symptoms may be debilitating if severe, and are generally unexpected.
[19] Insufficient buoyancy is a problem for divers who must ascend through the water column without assistance from a lifting platform, a surface tender, or something they can climb.
At worst the ascent rate may be a little fast near the surface and they will be unable to do a safety stop, but for divers with a significant decompression obligation, it can have more serious consequences.
Surface supplied divers who plan a dive with long decompression obligations usually carry weights which cannot easily be removed, to reduce the risk of accidentally losing them and becoming uncontrollably buoyant.
However, some inflator systems have a high flow rate, and if these valves stick fully open, the diver may not be able to dump fast enough to prevent being dragged upwards, at which stage a positive feedback of expansion of gas already in the BCD and possibly also the suit may become unrecoverable.
The other way of managing this problem is to mount the two inflator valve units together, and basically always assume that both bladders have gas in then, so always dump from both at the same time.
Underwater cutting and welding activities involve the use of live electrical conductors exposed to the water in the close proximity of the diver using them.
They also involve extreme heat and the generation of explosive gases, which may accumulate under obstacles to their free escape, and may detonate, causing pressure trauma to the diver.
[citation needed] Professional divers are often required to assist with the lifting and placement of large, massive objects underwater during the course of their employment.
Presence of tissue bubbles during autopsy is not necessarily an indication of DCS as gas will come out of solution when a body is decompressed by recovering to the surface.
The equipment, procedures and training associated with diving are specifically intended to prevent drowning, barotrauma and decompression sickness, and a fatality caused by one of these is an indication that the system failed in some way.
[13][37][38] The reaction to this problem includes the two extremes – The DIR philosophy of strict adherence to a standardised system of procedures and equipment, and not diving with anyone who does not use the same system, and the self-reliant route, where the diver elects to dive as if on their own, not relying on the buddy for assistance, and carrying sufficient equipment redundancy to manage reasonably foreseeable incidents unaided.
These divers may choose to dive solo rather than be burdened by a buddy of unknown competence or known incompetence,[37] but may be obstructed in this choice by legislation or terms and conditions of service.
This should be taken into account when presenting evidence, and investigators, expert witnesses, and the court or board of inquiry should ensure that opinions beyond the scope of their competence are specified as such so that they may be disregarded when making a judgement.