American Cave Diving Fatalities 1969-2007

When Blueprint for Survival was published, cave diver training agencies accepted that most cave diving accidents involved common risk factors, initially three, which were:

  • failing to dive with a continuous guideline to the surface
  • failing to limit the dive to 1/3 of the starting air volume and/or
  • diving beyond a safe depth for the type of gas being used.

Later, two additional rules were added: that divers entering caves should be trained, and each should have three sources of light capable of outlasting the dive.  These five rules now form the core of many cave diver courses. We reviewed 368 cave diving deaths to identify the rules most frequently violated in either trained or untrained divers. We hypothesized that different circumstances would apply to fatalities in these groups and argue that, for trained divers, the most important rules are associated with the most deaths. Greater emphasis given these rules during training might make cave diving even safer.

Methods

Cave-diving fatality records in the collection housed at DAN were reviewed and circumstances surrounding each death were classified using a process of root cause analysis. The four stages were the cause of death, the preceding event immediately before the death, the harmful action known to have occurred immediately prior to the preceding event, and the event that led to, or triggered, the harmful action.

Causes of death were taken from autopsy, medical examiner reports, or death certificates.  Circumstances preceding each death were classified according to evidence contained within each file, such as witness statements, police reports, equipment examinations, gas analysis reports, and other documents.  Cave diving safety rules that were broken were noted and when breaking a rule directly affected the chain of events then breaking that rule was also classed as relevant.  Merely being untrained was not deemed relevant if no other rules were broken and classed as relevant.

Each case was then again reviewed and the chain-of-events classified by a second reviewer and overall inter-rater agreement calculated for each of the four stages and for rules classed as broken or relevant.

Results

The final dataset comprised 368 divers who died whilst diving in caves between 1969 and 2007.  Males accounted for 95% (n=350).  Of those 368 divers, 329 (90%) died in caves within the USA, 14 (4%) in Mexico and nine (2%) in the Bahamas.  The remaining 16 divers (4%) were in 10 other countries.  Most of the deaths (n=287) within America occurred in Florida (87%), six (2%) died in Texas, six (2%) in Missouri, four (1%) in Georgia, four (1%) in Hawaii, and the remaining 22 divers (7%) were distributed across 16 other states. In Florida, three caves accounted for 111 of the 287 deaths (39%).  They were Peacock Slough (n=46, 16%), the Devil’s System (n=34, 12%) and Little River Spring (n=31, 11%).

Of the 275 divers whose occupation was known, the two most common were student (n=89, 32%) and US Military (n=34, 12%).  Professional divers and/or diving instructors accounted for 15 of the 275 (5%).  Of 199 divers for whom the level of recreational diving certification was known, 26 (13%) were rated diving instructors.  Marital status was known for 262 divers; 96 were single (37%), 154 married (59%) and 12 were divorced/widowed (5%).

Seventy-four divers (20%) were known to have been trained in cave-diving techniques while 208 (57%) were reported to have not completed cave diver training.  The training status of the remaining 86 (23%) divers could not be determined from information contained within the records.  The number of deaths per year appears to diminish over time, as shown in figure 1, whilst the proportion of divers that are trained appears to increase over the same period, as shown in figure 2.

Figure 1 - Number of reported cave diving deaths by year

 

Figure 2 - Proportion of cave diving deaths by trained divers, by year

 

Statistical tests indicated that trained divers tended to be older, to die at deeper depths, further into the cave, to carry more cylinders and to die alone, as shown in table 1.  The proportion of deaths where divers were known to have broken any of the five rules, and when breaking those rules contributed to each death, is also presented.

Table 1  Characteristics of Cave Divers by Training Status

 

Trained (n=74)

Untrained (n=208)

Overall (n=368)

Age in years        

37.5

26.7

28.8

Depth in feet        

155

74

91

Distance in feet    

750

258

374

Number of cylinders   n (%)

 

 

 

   Single cylinder

5    (7)

143 (69)

181  (49)

   More than one cylinder

37  (50)

17   (8)

65   (18)

   Total

42  (57)

160  (77)

246  (67)

Single or multiple      n (%)

 

 

 

   Single deaths

58 (78)

89 (43)

188 (51)

   Multiple deaths

16 (22)

119 (57)

180 (49)

Rules Broken             n (%)

 

 

 

   Thirds Rule         

19 (26)a

103 (50)a

152 (41)a

   Training Rule      

0 (0)a

208 (100)a

208 (57)a

   Line Rule            

9  (12)a

125 (60)a

162 (44)a

   Gas Rule             

12 (16)a

6 (3)a

25 (6.8)a

   Lights Rule         

7 (9)a

129 (62)a

167 (45)a

Broken and Relevant   n (%)

 

 

 

   Thirds Rule         

16 (84%)b

74 (72%)b

109 (72%)b

   Training Rule     

-

127 (61%)b

127 ( 61%)b

   Line Rule           

5 (56%)b

69 (55%)b

87 (54%)b

   Gas Rule            

3 (25%)b

2 (33%)b

8 (32%)b

   Lights Rule        

0 (0%)b

2 (2%)b

3 (2%)b

n=number of cases.  a=Percentage of divers who broke rule  b=Percentage of times broken rule deemed relevant

In addition to breaking the training rule, untrained divers were more likely than trained divers to have broken the continuous guideline rule, the three lights rule, and the thirds rule.  Amongst untrained divers it was more likely that breaking the rule of thirds would be relevant, and that breaking the continuous guideline rule would be relevant.  Trained divers were more likely to dive with a gas that was inappropriate for the depth, such as deep-air diving, but breaking that rule was not more likely to be relevant.

Training did not appear to change the likely cause of death.  Causes of death amongst trained and untrained divers are presented in table 2.  For those divers who drowned (n=294), the event that immediately preceded death is presented in table 3.  Untrained divers were more likely to have run out of air before drowning.  For those divers who ran out of air (n=211), the harmful actions that immediately preceded running out of air are shown in table 4.  Getting lost or making a dive with insufficient air preceded 76% of divers running out of air.  Circumstances that preceded getting lost (n=93) are presented in table 5 and circumstances preceding insufficient gas (n=67) are presented in table 6.

 

 

Table 2  Cause of Death by Training Status

Cause of death

Trained (n=74)

Untrained (n=208)

Overall (n=368)

Drowning

47 (64%)

180 (87%)

294 (80%)

AGE

7 (9%)

1 (0%)

11 (3%)

Cardiac

3 (4%)

1 (0%)

4 (1%)

Anoxia

1 (1%)

1 (0%)

2 (1%)

Unknown

16 (22%)

25 (12%)

57 (15%)

 

Table 3  Preceding Events by Training Status for Drowning

Preceding event

Trained (n=47)

Untrained (n=180)

Overall (n=294)

Ran out of air

31 (66%)

134 (74%)

211 (72%)

Did not run out of air

15 (32%)

31 (17%)

56 (19%)

Unknown

1 (2%)

15 (8%)

27 (9%)

 

Table 4  Harmful Actions Preceding Air Depletion by Training Status

Harmful action

Trained (n=31)

Untrained (n=134)

Overall (n=211)

Lost

14 (45%)

62 (46%)

93 (44%)

Insufficient gas

8 (26%)

49 (37%)

67 (32%)

Entangled

5 (16%)

9 (7%)

20 (9%)

Stuck in restriction

1 (3%)

3 (2%)

4 (2%)

Entrapped

1 (3%)

1 (1%)

2 (1%)

Equipment failure

1 (3%)

3 (2%)

7 (3%)

Unknown

1 (3%)

7 (5%)

18 (9%)

 

Table 5  Circumstances Preceding Getting Lost

Preceding getting lost

Trained (n=14)

Untrained (n=62)

Overall (n=93)

Silt-out

5 (36%)

33 (53%)

41 (44%)

No line

4 (29%)

27 (44%)

44 (47%)

Wrong turn

4 (29%)

2 (3%)

7 (8%)

Unknown

1 (7%)

0 (0%)

1 (1%)

 

Table 6  Circumstances that Preceded Diving with Insufficient Gas

Preceding insufficient gas

Trained (n=8)

Untrained (n=49)

Overall (n=67)

Poor gas planning

8 (100%)

48 (98%)

65 (97%)

Current

0 (0%)

1 (2%)

2 (3%)

Unknown

0 (0%)

0 (0%)

0 (0%)

Fitting it all into an analytical model, the main differences between trained and untrained divers were that older divers who died in caves were more likely to be trained cave-divers and that trained cave-divers were less likely to have died breaking the continuous line rule, and more likely to have died alone, rather than in a multiple fatality.  Dividing the dataset chronologically into two equal halves, early and late, and running a similar analysis, the differences between early and late divers were almost identical to the differences between trained and untrained cave-divers.

Discussion

That fewer cave diving deaths are recorded in the US each year is encouraging, though without knowing the number of participants, or number of dives made each year we can’t say the situation has improved in recent years, other than to say recently fewer cave diving deaths are being recorded annually by DAN.  With tougher access conditions, negative publicity following cave diving deaths, and the rising expense of cave diver training and equipment it could be argued that fewer divers are diving caves than were in previous years.  The three caves accounting for the most deaths now each have access restricted to trained divers only, so it is possible these access restrictions could be, at least in part, responsible for the drop in number of annual cave diving fatalities.  This would be in keeping with the Australian experience, where they had eleven cave diving deaths between 1969-73, tightened-up access in 1973 to trained divers only and have had just four deaths since. 

How to avoid getting lost and how to plan one’s gas needs are covered by most, if not all, cave diver training courses.  This could explain why untrained divers were more likely to have run out of air. Most divers who ran out of gas due to poor-planning (97%) should have had sufficient gas to escape the cave if they had turned at one third of their gas usage.  Put simply; regardless of training status, failing to plan adequately for one’s gas needs leads to running out of air and drowning.

Untrained divers were more likely to dive without a guideline, thus breaking one of the five “golden rules”, and were also more likely to have gotten lost in a silt-out.  Trained divers were more likely to have taken a “wrong turn”, perhaps because of the increasing complexity of long cave systems, now often with multiple guidelines and marked routes.

The gas-thirds rule was the most likely to become relevant when broken, followed by the training rule.  Trained divers broke the continuous guideline rule far less often than untrained divers (12% Vs 60%), though when they did it became relevant just as often (56% of the time) which should reinforce the importance of this rule to all who dive in caves.

Conclusion

In this study of cave diving fatalities, the main potential causes preceding death were a lack of continuous line to the surface and inadequate gas for the intended dive.  We recommend every cave diver give additional consideration to the guideline and thirds rules above all others.

 

This is a shortened version of the full-article Buzzacott P, Zeigler E, Denoble P, Vann R. American cave diving fatalities 1969-2007. 
International Journal of Aquatic Research and Education. 2009;3:162-177.  Furthermore, the editors of IJARE have expressed an interest in 
reviewing other cave-diving related research. This is a Divers Alert Network research project.

 

Author: 

Peter Buzzacott, Erin Zeigler, Petar Denoble and Richard Vann