This document discusses risk perception and safety in recreational diving. It presents several models for analyzing diving incidents, including cause-and-effect trees, Denoble's triggers, systems approaches, ETTO, and HFACS-D. The models show that most incidents do not have a single root cause but result from interactions between human, equipment, and environmental factors. Case studies demonstrate how heuristics and risk acceptance can contribute to errors. Overall, the document advocates for a systems view of causality, attitudinal changes in the diving community, and collaborative data sharing to improve safety.

1. ‘Obvious’ Errors:
Anything but Simple
Gareth Lock!
!
Cognitas Incident
Research and
Management

2. Background

3. Some humour…

4. Some humour…

5. OC Rec Case Study - Report
"Four divers were diving on a wreck to a maximum depth of
approximately 22m. One of the divers entered the wreck. Another
diver then went after him and found him unconscious with his
regulator in his mouth. He brought him out and recovered him to the
surface. He was lifted into the boat and the emergency services were
alerted. The diver was airlifted to hospital where he later died. The
diver had a 15l main cylinder and a 3l pony cylinder. After the event
the main cylinder was found to be full. A press report of the
Coroner's inquest suggests that the casualty had 'mixed up his air
supply tanks'. The cause of death was drowning."

6. OC Rec Case Study Introduction
❖ Club dive on wreck in 24m!
❖ Diver A 19st, 6’2”!
❖ BCD, 12L & pony, !
❖ 1st dive of the season, not dived for
10 months, 4 dives previous year!
❖ Buddy Checks carried out!
❖ OOG after 10mins!
❖ Separation!
❖ ‘Body’ found, CBL, sent up !
❖ Problems in recovering onto RHIB

7. Risk Perception/Acceptance vs Safety
❖ Risk is:!
❖ Relative!
❖ Personal (Voluntary)!
❖ Experience/Knowledge!
❖ Environment influenced!
❖ Goal influenced

8. Risk Perception/Acceptance vs Safety
❖ Risk is:!
❖ Relative!
❖ Personal (Voluntary)!
❖ Experience/Knowledge!
❖ Environment influenced!
❖ Goal influenced

9. Risk Perception/Acceptance vs Safety
❖ Risk is:!
❖ Relative!
❖ Personal (Voluntary)!
❖ Experience/Knowledge!
❖ Environment influenced!
❖ Goal influenced

10. Risk Perception/Acceptance vs Safety
❖ Risk is:!
❖ Relative!
❖ Personal (Voluntary)!
❖ Experience/Knowledge!
❖ Environment influenced!
❖ Goal influenced
❖ Is safety absence of risk?!
❖ Can we measure a negative?

11. Risk Perception/Acceptance vs Safety
❖ Risk is:!
❖ Relative!
❖ Personal (Voluntary)!
❖ Experience/Knowledge!
❖ Environment influenced!
❖ Goal influenced
❖ Is safety absence of risk?!
❖ Can we measure a negative?
❖ “Safety” is ability to sustain required
operations under both expected and
unexpected conditions.

12. Causality Models
❖ Cause and Effect Trees!
❖ Denoble's Triggers!
❖ Systems Approach !
❖ ETTO!
❖ HFACS-D

13. Small World Problem
How likely is it that any two persons, selected arbitrarily from a large population, can be linked via
common acquaintances and how long will the links be on average?

14. Small World Problem
In risk assessment, the problem is how likely it is that two events are indirectly coupled and how
many steps in between are required on average…The small world phenomenon demonstrates the
importance of this, namely that things (actions) that seemingly have no relation to each other still
may affect each other. - ETTO, Hollnagel, 2009

15. Cause and Effect Trees
❖ Simple, easy to understand!
❖ Bimodal - this happened,
caused that!
❖ Biases!
!
!
!
!

16. Cause and Effect Trees

17. Cause and Effect Trees

18. Cause and Effect Trees

19. Cause and Effect Trees

20. Cause and Effect Trees

21. Cause and Effect Trees

22. Hindsight bias!
Confirmation bias!
Cause and Effect Trees

23. Cause and Effect Trees
Action
1. Action based on event history and
current environment/situation

24. Cause and Effect Trees
Action
1. Action based on event history and
current environment/situation
!
!
Difference between the expected !
and unexpected outcome is not
clear cut!
3. Unexpected outcome - ‘Error’
2. Expected outcome - ‘Good’

25. Cause and Effect Trees
Action
Outcome of Previous Action
4. Hindsight provides "
feedback of ‘correct’ action
1. Action based on event history and
current environment/situation
!
!
Difference between the expected !
and unexpected outcome is not
clear cut!
3. Unexpected outcome - ‘Error’
2. Expected outcome - ‘Good’

26. Cause and Effect Trees
Action
Outcome of Previous Action
4. Hindsight provides "
feedback of ‘correct’ action
1. Action based on event history and
current environment/situation
!
!
Difference between the expected !
and unexpected outcome is not
clear cut!
3. Unexpected outcome - ‘Error’
2. Expected outcome - ‘Good’
4. Hindsight provides "
incorrect feedback of action "
if they thought outcome was ‘Good’
or

27. Denoble's Triggers
❖ 947 fatalities analysed

28. Denoble's Triggers
❖ 947 fatalities analysed
❖ Triggers!
❖ OOA (41%)!
❖ Entrapment (20%)!
❖ Equipment
Problems (15%)
Denoble, P.J., Caruso, J.L., Dear, G.d.e. .L., Pieper, C.F. & Vann, R.D., 2008, Common causes of open-circuit recreational diving fatalities, Undersea & hyperbaric medicine : journal of the
Undersea and Hyperbaric Medical Society, Inc, 35(6), pp. 393-406

29. Denoble's Triggers
❖ 947 fatalities analysed
❖ Triggers!
❖ OOA (41%)!
❖ Entrapment (20%)!
❖ Equipment
Problems (15%)
❖ What, not why
Denoble, P.J., Caruso, J.L., Dear, G.d.e. .L., Pieper, C.F. & Vann, R.D., 2008, Common causes of open-circuit recreational diving fatalities, Undersea & hyperbaric medicine : journal of the
Undersea and Hyperbaric Medical Society, Inc, 35(6), pp. 393-406

30. Systems Approach
Technological Failure Human Failure Organisational Failure
1900 1950 2000
Simple Linear Models!
Independent Causes
Complex Linear Models!
Active and Latent
Non-Linear Models!
Tractable/Intractable
Dynamic Complexity
Adapted from Hollnagel, E., 2009, The ETTO Principle:

31. Efficiency Thoroughness Trade Off (ETTO)
❖ ETTO!
❖ Heuristics!
❖ Shortcuts

32. Efficiency Thoroughness Trade Off (ETTO)
❖ ETTO!
❖ Heuristics!
❖ Shortcuts
❖ Performance Variability!
❖ Approximations!
❖ Normalisation of Deviance

33. Efficiency Thoroughness Trade Off (ETTO)
Examples of Heuristics
• Looks fine"
• Not really important"
• Normally OK, no need to check"
• I’ve done it millions of times before"
• Will be checked by someone else"
• Has been checked by someone else"
• This way is much quicker"
• No time (or resource) to do it now"
• Can’t remember how to do it"
• We always do it this way"
• Looks like X, so must be X

34. HFACS-Diving

35. HFACS-Diving
❖ Based on HFACS Model

36. HFACS-Diving
❖ Based on HFACS Model
❖ Constructed after reviewing 18
pieces of literature - 232 factors!
❖ Validated by 13 SMEs
Poor
decision
to
con,nue
dive
Incorrect
assembly
of
CCR/scrubber
packing
Incorrect
maintenance
of
pO2
(eCCR)

37. HFACS-Diving
❖ Based on HFACS Model
❖ Constructed after reviewing 18
pieces of literature - 232 factors!
❖ Validated by 13 SMEs
❖ 96 factors!
❖ Rules/Violations!
❖ 5 equipment based!
❖ Fiscal drivers*!
❖ Latent Medical*"
❖ Direct Contravention of Trg*
Poor
decision
to
con,nue
dive
Incorrect
assembly
of
CCR/scrubber
packing
Incorrect
maintenance
of
pO2
(eCCR)

38. OC Rec Review Incident Case Study
❖ General Fitness!
❖ Dive and Rescue!
❖ ‘Dived Up’!
❖ Checks and Config!
❖ OOA response!
❖ Separated!
❖ Body recovered

39. OC Rec Review Incident Case Study
Skill Based Errors
(Incorrect In Water
Skills)!
Failure to Monitor Gauge and end dive when reached mininum gas pressure
e.g. surface with 50bar/500psi
Incorrect response for Out of Air (OOA)
Equipment problems (use of, not failure of)
Knowledge Based
Failure to Understand Equipment usage!
Failure to Complete Pre-Dive Buddy/Self Checks
Condition of Operator
(Physiological State)
Drug or Alcohol Intoxication
Personal Readiness
(Training/Skills)
Insufficient Training (Lack of currency of skills to ensure that they are upto
date, 'Dive Fit')

40. HFACS-D - Data as at 11/2/14

41. HFACS-D - Data as at 11/2/14
❖ Incidents (n=341)!
❖ 31% physical OOG/below agency minimums!
❖ 9% uncontrolled buoyant ascents!
❖ 23% unplanned separation

42. HFACS-D - Data as at 11/2/14
❖ Incidents (n=341)!
❖ 31% physical OOG/below agency minimums!
❖ 9% uncontrolled buoyant ascents!
❖ 23% unplanned separation
❖ Dive plan deviation - 18%

43. HFACS-D - Data as at 11/2/14
❖ Incidents (n=341)!
❖ 31% physical OOG/below agency minimums!
❖ 9% uncontrolled buoyant ascents!
❖ 23% unplanned separation
❖ Dive plan deviation - 18%
❖ Decision to continue when should have ended - 23%

44. HFACS-D - Data as at 11/2/14

45. ❖ ETTO!
❖ Looks fine to me 10%!
❖ Normally worked/Worked before 24%
HFACS-D - Data as at 11/2/14

46. ❖ ETTO!
❖ Looks fine to me 10%!
❖ Normally worked/Worked before 24%
❖ Attitude!
❖ Complacency 41%, Lack of Situational Awareness 32%!
❖ Risk Perception/Acceptance 50%!
❖ Behaviour 20% not changed
HFACS-D - Data as at 11/2/14

47. ❖ ETTO!
❖ Looks fine to me 10%!
❖ Normally worked/Worked before 24%
❖ Attitude!
❖ Complacency 41%, Lack of Situational Awareness 32%!
❖ Risk Perception/Acceptance 50%!
❖ Behaviour 20% not changed
❖ Social!
❖ 8-12% direct, indirect or fiscal pressures
HFACS-D - Data as at 11/2/14

48. How to Improve Things
❖ Attitudinal Changes Essential!
❖ Stop Throwing Rocks at
Those Who Make Mistakes

49. How to Improve Things
❖ Attitudinal Changes Essential!
❖ Stop Throwing Rocks at
Those Who Make Mistakes
❖ Promote Personal
Responsibility!
❖ We ALL make mistakes,
most of them our own doing!
❖ Group Polarisation/Risky
Shift

50. How to Improve Things
❖ 'Just Culture'!
❖ 'Who Decides'!
❖ Recreational vs Voluntary
Instruction vs Professional
Instruction

51. How to Improve Things
❖ 'Just Culture'!
❖ 'Who Decides'!
❖ Recreational vs Voluntary
Instruction vs Professional
Instruction

52. How to Improve Things
❖ Work Together!
❖ Improved Reporting !
❖ Sharing of Data!
❖ Common Models
All the Information Possible to be Known
Diver’s Knowledge
Friends’s Knowledge
Researcher’s Knowledge
http://www.divingincidents.org.uk
@DISRC #DISMS

53. Summary
❖ Risk and Safety are compromises!
❖ Too many factors to use simple
models!
❖ No one ‘root cause’!
❖ Need detailed narratives!
❖ We can improve things…

54. http://www.cognitas.org.uk
http://www.divingincidents.org.uk
@DISRC #DISMS
“What good is hindsight if we supposedly learn something
but don’t apply it to our own/community’s foresight?”