Cave Diving Learning Curve

The Cave Diving Learning Curve is shaped by experience, training, and careful decision-making. This analysis examines fatal British cave diving incidents between 1980 and 2005 to understand how experience influences safety and survival in the underground environment.

The study reviewed nine fatal cave diving incidents recorded over a 26-year period. The overall fatality rate was estimated at 1 in 3,286 dives. However, experience was the most significant factor affecting survival.

Experienced divers were far more likely to survive a cave dive than inexperienced divers. For experienced divers, inadequate line management represented the greatest risk. For inexperienced divers, the main hazard was insufficient training and preparation.

Cave diving safety improved considerably during this period, particularly for experienced divers. An experienced cave diver was estimated to be 39 times more likely to survive a dive than an experienced diver from 26 years earlier.

However, improvements in safety did not occur at the same rate among newer divers. Further work remains necessary to understand the challenges faced by inexperienced cave divers and to develop training systems that help divers progress safely through the Cave Diving Learning Curve.

Method of Analysis

Researchers collected information using a standardised format to analyse fatal incidents involving divers who intentionally entered the overhead environment of natural caves in Britain, excluding Ireland.

The study included only cave diving incidents involving breathing apparatus. It excluded open-water training accidents, breath-hold diving incidents, mine diving, and incidents outside mainland Britain.

Information was gathered from published reports and from accounts provided by people involved in the incidents.

The following information was recorded for each incident:

• Name
• Age
• Date of incident
• Location
• CDG qualified diver status
• CDG membership status
• Estimated previous experience of more than 45 dives
• Whether line management contributed to the incident
• Whether equipment failure contributed
• Whether training contributed
• Other contributing factors
• A summary of the incident and probable causes

Statistical Considerations

The results require careful interpretation. The number of fatal incidents was small, and several factors influence the accuracy of the analysis.

One major factor is the period covered by the study. Cave diving equipment, training standards, and exploration techniques changed significantly between 1980 and 2005. These improvements reduced the likelihood of fatal incidents.

The small number of incidents also creates statistical limitations. While incident rates provide useful comparisons, they contain an unknown margin of error.

Training standards also improved during this period, allowing new divers to begin their progression through the Cave Diving Learning Curve with better preparation and safer practices.

Incident rates must also be interpreted correctly. A fatality rate of 1 in 3,286 dives does not mean that the 3,287th dive will be fatal. Instead, it means that if 3,286 people each completed one identical dive, statistically one fatality might be expected.

The study is also limited by the available information. Although the British cave diving community is small and close-knit, some details surrounding incidents remain incomplete. Artificial cave environments such as mines were excluded to maintain a consistent dataset.

Fatal Incidents and Contributing Factors

Incidents From CDG Newsletters

1980 – Bull Pot of the Witches

Ian Plant lost the line in Sump 2 of Bull Pot of the Witches and ran out of air before locating the exit through a complex section of cave in poor visibility.

1980 – Keld Head

Four divers undertook a training dive at Keld Head. Mark Woodhouse, an inexperienced diver, became entangled in the line near a water-filled airbell approximately 100m from the entrance.

After freeing himself, he surfaced in the airbell in a state of panic. Another diver nearby attempted to assist but first had to correct his own buoyancy.

By the time assistance was possible, Woodhouse had returned into the sump. The second diver later found him unconscious with his mouthpiece removed. Despite recovery efforts, he could not be saved.

1981 – Wookey Hole

Keith Potter, a trainee diver, died during a training dive at Wookey Hole. He appears to have lost his mouthpiece shortly before reaching the surface in Chamber 20.

1985 – Hurtle Pot

Derek Crossland, an experienced diver, drowned approximately 14m from the surface during a routine dive. Later equipment testing found no defects, and the exact cause remains uncertain.

1988 – Barbondale

Nick Whaite, aged 18 and relatively inexperienced, became trapped while attempting to explore a tight, previously unknown sump using a base-fed line. The sump was later pumped out and the body recovered.

1992 – Joint Hole

Martin McMahon failed to return from a routine dive to the first airbell. He was later found near the entrance on the guideline with air remaining in his cylinders. No obvious equipment problems were identified.

1994 – Birkwith Cave

Trevor Kemp, an inexperienced diver, disappeared during a through trip from Old Ing to Birkwith. He was found the following day approximately halfway through the sump near a tight “letterbox” restriction.

His equipment functioned correctly when examined afterwards, although the cylinder contents gauge arrangement meant pressure could not be checked during the dive.

1998 – Ogof Pont Y Meirw

Peter Fowler drowned while returning from exploration beyond the first sump. The guideline had become trapped in undercuts, and he was found a short distance from the entrance with no remaining air.

Later inspection identified a fault with one demand valve.

2005 – Low Birkwith Cave

Colin Pryer, an experienced diver, was revisiting a low, silty cave passage that had last been extended during the 1970s. He became trapped by old loose line and exhausted his air supply before freeing himself.

Analysis of Experience and Safety

The estimated total amount of diving performed between 1980 and 2004 is 29,149 man-dives of which 1,140 were conducted in 1980.  Information for all dives in 2005 was taken from CDG Newsletters 154 to 157 which reported a total of 335 man-dives for the year.  Using the reporting rate estimate of 78%, the estimate for the total amount of diving in 2005 is 429 man-dives.  The total amount of diving for 1980 to 2005 is 29,578 man-dives.  The total amount of diving for 1981 to 2005 is 28,438 man-dives.

It has been estimated that new cave divers performed 6,750 man-dives between 1980 and 2004.  The full estimate from 1980 to 2005 would therefore be 7,020 man-dives.  The estimate from 1981 to 2005 would therefore be 6,750 man-dives.

Analysis of Incident Rates

Incident rates have been calculated and are presented below.

The time between the first and the last incident has been identified as a confounding factor.  Line management was identified as a major problem in 1980 and a Technical Review was published to address this issue [Yeadon, 1981].  Since then the quality of line management has improved and a sub-group of dives from 1981 to 2005 has been analysed to give an incident rate that may be more appropriate to modern circumstances.

Experience has been identified as a variable.  Three interpretations of experience were collected during the data collection phase.  Membership of the CDG is not used as a definition of experienced for the purposes of this analysis.  Both being a Qualified Diver and having completed an estimated 45 dives are analysed as being an experienced diver.

Previous work [Brock, 2005] has identified that line management, equipment failure and training are the three most important hazards faced by British cave divers.  Incident rates are reported for these three factors.

Rates of Fatal Accidents

Discussion

The overall fatal incident rate was estimated at 1 in 3,286 dives. However, the figures become more meaningful when experience levels are considered.

The greatest difference occurred between experienced and inexperienced divers.

CDG qualified divers had an estimated fatal incident rate of 1 in 28,438 dives, compared with 1 in 1,125 dives for unqualified divers.

This suggests that qualified divers were approximately 25 times more likely to survive a cave dive than inexperienced divers.

A similar effect was found by the HSE when examining open water diving.  They found that:

“There are a small number of repeated causes associated with the majority of fatalities.  If these causes are eliminated then the number of fatalities would have fallen from 286 to 8“.  This equates to a 36-fold difference in the incident rates between true accidents and fatal incidents involving repeat causes.

The last quantitative analysis of fatalities conducted by the CDG covered the period 1957 to 1978 and indicated an overall fatal incident rate of 1 in 620 dives.  Excluding the non-cave and non-British dives there were 6 fatalities from 4338 dives, of which 3 were experienced divers and 3 were inexperienced divers.  The overall fatality rate was therefore 1 in 723 dives.  There was no obvious difference between the number of fatal incidents for experienced and in-experienced divers.  The analysis did not report the proportion of the 4338 dives that were conducted by inexperienced and experienced divers so the assumption is made that an equal number of dives were performed by both subgroups.

Safety and Experience

In the 26 years between the two analyses of cave diving figures there has been a great step forward in the safety of experienced divers.  The fatal incident rate of 1957 to 1978 was 39 times higher for experienced divers than for their counterparts 26 years later.  Unfortunately the same improvements for safety have not been made for inexperienced divers for whom the fatal incident rate improved by only a factor of 1.6.  Although there are sampling and assumption errors, there is no evidence of a significant improvement in the safety of inexperienced cave divers over the last 26 years.

Three main causal factors were analysed; line management, equipment failure and training.  Equipment failure and training were not major factors in either of the recorded incidents for experienced divers whereas line management figured in both.  Experienced divers clearly need to take account of all hazards affecting cave diving but should pay particular attention to line management.

All factors contributed to the incidents for inexperienced divers and it comes as no surprise that training was the predominant factor.  The key message for inexperienced divers is simple: proper training and qualification are essential steps in progressing safely.  

As this group of divers is at a significantly higher risk of a fatal incident, the training should be controlled by very stringent safety standards.  There was also a high incidence of uncategorized contributory factors recorded as “other” affecting inexperienced divers.  A number of factors fell into this category such as panic or irrational decisions.  Brandt claims that anxiety or other psychological problems affect 12% of non-fatal incidents.  It is probable that inexperienced divers are far more susceptible to these issues than experienced divers and more work should be done in this area.

Conclusions

Fatal cave diving incidents are fortunately rare, making statistical comparisons difficult. However, the available evidence shows that cave diving safety improved significantly for experienced divers between 1980 and 2005.

The same improvements were not seen among inexperienced divers.

Experience, structured training, and disciplined procedures remain the most important factors in reducing risk underground.

Cave diving will always involve hazards, but careful progression through the Cave Diving Learning Curve allows divers to explore challenging environments while managing those risks responsibly.