Ladd G. Treatment of psychological injury after a scuba-diving fatality.
Diving and Hyperbaric Medicine. 2007; 37: 36-39.

Abstract: After the death of a student during an ocean scuba training dive, the student's diving instructor was suffering from Acute Stress Disorder, a post-traumatic stress reaction. The treatment of the instructor's distress using a combination of two recognized trauma therapies: Eye movement desensitization and reprocessing (EMDR) and cognitive-behaviour therapy (CBT) is described. Improvement was noted after four treatment sessions. The instructor reported further improvement at a two-month follow-up and the positive effects were maintained nineteen months later.

Raglin JS, Stegner AJ. Psychobiological aspects of panic in SCBA and SCUBA. G.
International Journal of Sport and Exercise Psychology. 2005; 3: 446-454.

Abstract: This review focuses on a series of survey and experimental investigations, led by Professor William P. Morgan, designed to examine the role of panic and anxiety in the etiology of diving-related accidents and deaths. A significant proportion of scuba fatalities have been attributed to panicking while submerged, but these estimates should be considered conservative at best. Morgan's work has demonstrated that most divers report experiencing panic or near-panic incidents at some point in their diving careers and that the phenomenon is not limited to novice or inexperienced divers. Trait anxiety has proven to be a reliable predictor of those individuals prone to panic behavior while wearing a self-contained breathing apparatus, both above and underneath water. Additional investigations have suggested that environmental influences, such as water temperature and thermal apparel, could also be critical factors in the development of panic while diving. Employing a psychobiological perspective, Morgan's research has made an impressive and indelible contribution to the future safety of scuba divers and to the field of sport psychology.

Slosman DO, de Ribaupierre S, Chicherio C, Ludwig C, Montandon M-L, Allaoua M, Genton L, Pichard C, Grousset A, Mayer E, Annoni J-M, de Ribaupierre A. Negative neurofunctional effects of frequency, depth and environment in recreational scuba diving: the Geneva "memory dive" study.
British Journal of Sports Medicine. 2004; 38: 108-114.

Abstract: Objectives: To explore relationships between scuba diving activity, brain, and behaviour, and more specifically between global cerebral blood flow (CBF) or cognitive performance and total, annual, or last 6 months' frequencies, for standard dives or dives performed below 40 m, in cold water or warm sea geographical environments.
Methods: A prospective cohort study was used to examine divers from diving clubs around Lac Le _ man and Geneva University Hospital. The subjects were 215 healthy recreational divers (diving with self-contained underwater breathing apparatus). Main outcome measures were: measurement of global CBF by 133Xe SPECT (single photon emission computed tomography); psychometric and neuropsychological tests to assess perceptual-motor abilities, spatial discrimination, attentional resources, executive functioning, and memory; evaluation of scuba diving activity by questionnaire focusing on number and maximum depth of dives and geographical site of the diving activity (cold water v warm water); and body composition analyses (BMI).
Results: (1) A negative influence of depth of dives on CBF and its combined effect with BMI and age was found. (2) A specific diving environment (more than 80% of dives in lakes) had a negative effect on CBF. (3) Depth and number of dives had a negative influence on cognitive performance (speed, flexibility and inhibition processing in attentional tasks). (4) A negative effect of a specific diving environment on cognitive performance (flexibility and inhibition components) was found.
Conclusions: Scuba diving may have long-term negative neurofunctional effects when performed in extreme conditions, namely cold water, with more than 100 dives per year, and maximal depth below 40 m.

Miller G, Taubman-Ben-Ari O. Scuba diving risk taking--a terror management theory perspective.
Journal of Sport & Exercise Psychology. 2004; 26: 269-282.

Abstract: This study examined, from a Terror Management Theory (TMT) perspective, the effects of death reminders on the tendency to take risks in diving. All participants (N = 124) completed Rosenberg's self-esteem scale and a diving related self-efficacy questionnaire. Then half of them were exposed to a mortality salience induction and the other half to the control condition. The dependent variable was self-reported intentions to take risks in diving. Findings showed that mortality salience led to greater willingness to take risks in diving vs. control condition, but only among divers with low self-esteem and low diving related self-efficacy. In addition, mortality salience led to less willingness to take risks in diving vs. the control condition only for low self-esteem divers who possessed high diving related self-efficacy. However, no effects were found for high self-esteem persons. The results are discussed in view of the self-enhancing mechanisms proposed by TMT, offering practical implications regarding the need to increase divers' self-esteem and self-efficacy as a preventive strategy.

Morgan WP, Raglin JS, O'Connor PJ. Trait anxiety predicts panic behavior in beginning scuba students.
International Journal of Sports Medicine. 2004; 25: 314-22.

Abstract: Recreational scuba diving is associated with a significant number of fatalities and decompression illnesses each year, and there is evidence that permanent neuropsychological injury can occur in divers. There is also evidence that the principal cause of decompression illness and fatalities in divers is rapid ascent, and it appears that the primary stimulus for rapid ascent is panic. The primary purpose of this investigation was to evaluate the extent to which an objective measure of trait anxiety could be effective in predicting panic behavior in students undergoing scuba training. Trait anxiety was assessed at the outset of scuba instruction in 42 students, and the instructor recorded instances of panic behavior during the 4-month course. It was predicted that individuals scoring 39 or greater on the trait anxiety sub-scale of the State-Trait Anxiety Inventory would be more likely to experience panic behavior than individuals with scores below this cut-off. Predictions and actual recordings of panic behavior were performed independently using a blinded paradigm. Eleven of the students exhibited panic behavior on two or more occasions during the instruction, and 35 of 42 (83 %) predictions were accurate (p < 0.001). It is concluded that an objective measure of trait anxiety can be employed a priori for prediction of panic behavior in beginning scuba students.

Ramírez J, Villaverde C, Oltras C, Ruíz-Villaverde R, Sánchez-Caravaca M. Levels of ACTH and β-endorphin in the response to stress from open sea scuba diving to 25 m (3.5 ATA). A field study.
International Journal of Sport Psychology. 2004; 35: 1-12.

Abstract: To investigate the endocrine response (ACTH and beta-endorphin) to scuba diving in the open sea, in individuals with different levels of training. Materials and methods: Samples of blood and urine were obtained from two groups of divers: El (n=6) had over 4 years' experience, with frequent dives below 35 m; E2 (n=6) had 3 years' experience or less and had not dived below 15 m. A sedentary control group (n=11), who did not practice sports, was evaluated to establish basal measurements. The test consisted of submersion in the open sea to a depth of 25m (3.5 ATA).
Results: In El, there was a presubmersion increase in plasma levels of ACTH and beta-endorphin (p<0.05) and a significant decrease after the test. In E2, levels of these hormones were significantly higher after submersion (p<0.05).
Discussion: These changes are related to an anticipation phenomenon in the El group, in which adaptive mechanisms to hyperbaric submersion come into play, due to their greater experience than the E2 group. The submersion itself did not present an additional stimulus for the members of the El group, which explains the fall in hormone levels observed after the test.

Watson AE, Pulford BD. Personality differences in high risk sports amateurs and instructors.
Perceptual & Motor Skills. 2004; 99: 83-94.

Abstract: This study investigated the personality differences of 21 amateurs and 20 instructors who participated in the high risk sports of skydiving, hang-gliding, paragliding, scuba diving, microlighting, and rock climbing, versus those who did not. 38 men and 28 women (M age = 32.6 yr., 51)= 10.0) were assessed using the Eysenck Personality Questionnaire-Revised, the General Health Questionnaire, the Generalised Self-efficacy Scale, and a Type A/B personality measure. Instructors and Amateurs scored significantly higher on Extroversion and lower on Neuroticism than Nonparticipants; however, they differed from each other on the General Health Questionnaire and Type A/B personality scores. Amateurs scored significantly higher on Psychoticism and Self-efficacy than Instructors and Nonparticipants. In conclusion, these test scores suggest that people who are attracted to high risk sports tend to be at the extroverted and emotionally stable end of the scale, with a tendency to exhibit Type A characteristics; however, Instructors' scores on Psychoticism and Self-efficacy are more akin to those of Nonparticipants.

Ness GJ, Macaskill N. Preventing PTSD: the value of inner resourcefulness and a sense of personal control of a situation. Is it a matter of problem-solving or anxiety management?
Behavioural and Cognitive Psychotherapy. 2003; 31: 463-466.

Abstract: The accounts of five subjects who survived life threatening experiences without the development of PTSD were examined, focusing on the coping strategies and cognitions described in these situations. The study aimed to determine whether there was a common pattern of response amongst subjects in these situations similar to the cognitive patterns described by the senior author of the previous case study (Ness & Macaskill, 2000) who survived a near drowning experience without the development of PTSD. In the search for common coping strategies all five respondents in the study completed the Locus of Control Scale (Rotter, 1966) and the Self-Control Schedule (Fisher & Reason, 1988). All five respondents demonstrated the use of problem solving as their main cognitive strategy, utilizing specific information from their previous experience relevant to their life-threatening situation. Respondents did not appear to rely on coping strategies aimed at the management of acute anxiety symptomatology. There was no common pattern among respondents in profiles on the Self-Control Schedule or the Locus of Control Scale. The possible implications of this case series study are discussed in relation to opportunities for the prevention of PTSD, the use of debriefing and the treatment of post-traumatic stress.

Anegg U, Dietmaier G, Maier A, Tomaselli F, Gabor S, Kallus KW, Smolle-Jüttner FM. Stress-induced hormonal and mood responses in scuba divers: A field study.
Life Sciences, 2002; 70: 2721-2734.

Abstract: Examined the relationship between self-reported emotional state and the hormonal and respiratory responses of scuba divers during stressful and non-stressful (recreational) dives. The 15-55 yr old male Ss were divided into 2 groups of 7 divers each with opposite stress coping strategies. Measured parameters included total air consumption, plasma hormone levels of epinephrine, norepinephrine and prolactin, and saliva cortisol levels. Results show that prolactin was a hormonal marker with a significant increase in the sub-group of stress-controllers. Along with the self-reported emotional conditions under immersion, these data suggest that an increased prolactin level reflects a state of elevated physical and mental activation and vigilance. Facing a stressful situation, Ss with more emotional concern and the tendency to surrender react by "blunted responses" showed significantly lower elevations of prolactin levels, in contrast to Ss with the opposite psychological features. The other somatic parameters (epinephrine, norepinephrine) showed significant increases during and after dives (with the exception of saliva cortisol), but without any significant group difference.

Ladd G, Stepan V, Stevens L. The Abacus Project: establishing the risk of recreational scuba death and decompression illness.
South Pacific Underwater Medical Society Journal. 2002; 32: 124-128.

Abstract: In order to establish the relative risk of death and non-fatal decompression illness (DCI) in recreational scuba diving in British Columbia (BC), Canada, a field survey was conducted. For 14 months, every dive shop and charter operator in the province of BC was asked to count the number of scuba tanks that were filled for use in recreational scuba diving. For the same 14 month period, hyperbaric chambers reported the number of BC divers treated for non-fatal DCI and the provincial coroners records were reviewed for scuba fatalities. Over the 14 months that scuba tank fill information was collected, an average of 65% (range: 60-71%) of the fill stations reported. Death and DCI incidence rates were calculated based on the 146,291 fills reported by the participating stations. During this same period there were 3 fatalities and 14 cases of non-fatal DCI. The incidence of recreational scuba death was 0.002% (2.05/100,000 dives). The incidence of non-fatal DCI was 0.010% (9.57/100,000 dives). Results are discussed in light of this being the first time a reasonably reliable measure of diving activity has been achieved in a large geographic area over an extended time period.

Taylor D, O'Toole KS, Auble TE, Ryan CM, Sherman DR. The psychometric and cardiac effects of pseudoephedrine in the hyperbaric environment.
Pharmacotherapy. 2000; 20: 1045-1050.

Abstract: Study Objectives: To examine the psychometric and cardiac effects of pseudoephedrine at 1 and 3 atmospheres (atm) of pressure (0 and 66 feet of sea water, respectively), and to make recommendations about the agent's safety in the diving environment.
Design: Double-blind, placebo-controlled, crossover study.
Setting: Monoplace hyperbaric chamber of a university hospital.
Subjects: Thirty active divers (mean age 38 yrs).
Intervention: A bank of seven tests was used to assess cognitive function during four different simulated dive combinations: placebo-1 atm, placebo-3 atm, pseudoephedrine-1 atm, and pseudoephedrine-3 atm.
Measurements and Main Results: Heart rate and cardiac rhythm were recorded during all dives. Repeated-measures analysis of variance was used to analyze the effects of pseudoephedrine, depth, and drug-depth interaction. No significant, independent effects of pseudoephedrine were seen on any of the seven psychometric test scores (p>0.05), although the drug tended to increase anxiety scores (p=0.092). Depth resulted in a significant increase in anxiety scores (p=0.021) and a significant decrease in verbal fluency test scores (p=0.041); it had no significant effects on the other five psychometric tests (p>0.05). Pseudoephedrine caused a significant increase (p=0.036) in mean heart rate, and depth caused a significant decrease (p=0.013). Neither pseudoephedrine nor depth affected cardiac rhythm.
Conclusion: Pseudoephedrine does not cause significant alterations in psychometric performance at 3 atm of pressure that might increase the risk of diving. Depth causes significant adverse effects on anxiety levels and semantic memory at 3 atm. Pseudoephedrine and depth have significant but opposite effects on heart rate; although, these effects are unlikely to be clinically significant during diving. It is unlikely that pseudoephedrine adds significant risk to the diver.

Wang J, Akirav I, Richter-Levin G. Short-term behavioral and electrophysiological consequences of underwater trauma.
Physiology & Behavior. 2000; 70: 327-332.

Abstract: In a previous work we found that a 30-s underwater trauma, following 8 days of training for a spatial memory task in the water maze, resulted in poor performance in the spatial memory task at both 1 h and 3 weeks after the trauma. Here we found that compared with naive animals and animals that were trained for the spatial learning task but were not traumatized, the traumatized rats showed impaired performance in a spatial learning task in the water maze 20 min after the trauma and a reduced level of dentate gyrus long-term potentiation (LTP) 40 min after high-frequency stimulation to the perforant path. We also found a positive correlation between the behavioral performance and hippocampal plasticity. The reduced ability to induce LTP suggests that the trauma-related behavioral impairment is mediated by hippocampal dependent processes. The underwater trauma may provide an important and potentially powerful model for understanding the mechanisms underlying the relationship between stress, cognition, and learning.

Raglin JS. Psychobiological antecedents of panic in scuba diving.
Performance in Extreme Environments. 1998; 3: 26-29.

Abstract: While scuba diving has been promoted as a safe activity, it is not free from risk. From 1970 to 1993, the number of yearly scuba diving fatalities in the US has averaged 104. Despite improvements in training and equipment design, this figure has remained essentially unchanged, averaging 101 for 1994 and 1995, according to the most recent data available. Depending on the estimate of active recreational divers, the relative risk of death while diving may be as high as 3.84 per 100,000 divers. While the majority of these deaths can be ascribed to known causes such as injury or equipment failure, the precipitating factors in up to 40% of fatalities remains unknown. Many of these unexplained deaths have been attributed to psychological variables, in both recreational and professional diving. In particular, anxiety and panic are widely regarded to be the primarily psychological factors in diving accidents and fatalities. This article summarizes (1) survey research on panic in scuba diving, (2) psychological approaches to predicting panic in stressful exercise settings, and (3) psychobiological studies of anxiety and physical performance. Despite views to the contrary, panic behavior is not a rare occurrence in scuba diving.

Richter-Levin G. Acute and long-term behavioral correlates of underwater trauma - potential relevance to stress and post-stress syndromes.
Psychiatry Research. 1998; 79: 73-83.

Abstract: As a consequence of a brief but significantly extreme stressor, an individual will experience a stress response, which may sometimes develop into Acute Stress Disorder (ASD) or Post-Traumatic Stress Disorder (PTSD). Though a rat model for ASD and PTSD is not expected to encompass the richness and complexity of the disorders in humans, it will enable the study of the common underlying mechanisms that generate the disorders, the study of pre-trauma etiological aspects of the disorders and the screening of drugs with potential relevance to the treatment of the disorders. One well-documented aspect of PTSD is the enhancing influence of contextual elements on the appearance of symptoms of the post-stress trauma. To exploit this effect, we have chosen to assess the effects of an underwater trauma in the Morris water maze since the effects of such trauma on memory and attention can be later evaluated in the context of the trauma. At both 1 h and 3 weeks after the trauma, significant behavioral deficits were observed in the water maze. The effects of the underwater trauma on the performance of rats in the water maze were context specific. Underwater trauma in a different (out-of-context) water container had no effects on the ability of rats to perform a spatial memory task in the water maze. An elevated level of anxiety was found in the plus maze test, independently of whether the trauma was performed in the water maze or in a different (out-of-context) water container. The results indicate that a within-context underwater trauma has both acute and lasting behavioral consequences which can be assessed using a spatial memory test in the context of the trauma. The results are discussed in relation to their relevance to stress and PTSD.

Terry PC, Mayer JL, Howe, BL. Effectiveness of a mental training program for novice scuba divers.
Journal of Applied & Sport Psychology. 1998; 10: 251-267.

Abstract: Assessed the effects of a mental training program on state anxiety, respiration rate and performance of novice scuba divers (mean age 30.3 yrs). In addition to scuba training, 15 Ss received an audiotaped mental training program designed to reduce anxiety and improve diving performance, 15 Ss in a placebo-control group followed the same procedures except that their audiotape contained general information about scuba diving, and 14 control Ss received only scuba training. Anxiety and panic in recreational scuba divers.

Morgan WP. Anxiety and panic in recreational scuba divers.
Human Performance in Extreme Environments. 1996; 1: 20-35.

Abstract: Explores issues concerning the role of anxiety and panic in recreational diving fatalities. A review of the accident and mortality statistics occurring within the dive community is presented and the classifications associated with such fatalities are addressed. The author offers an understanding of the behavioral and performance issues associated with operating a self-contained underwater breathing apparatus in the underwater environment. Findings are employed from research with populations (firefighters and athletes) operating in similar conditions with a self-contained breathing apparatus, and how stress and anxiety can mediate the behavior and performance of users operating such systems are illustrated. Psychological characteristics of divers are explored, along with their overall anxiety levels as compared to other populations. It is argued that this research illuminates the need for implementing a psychological component to the curriculum of open-water certification programs to decrease the risks associated with the panic and anxiety of recreational divers. Psychological interventions are discussed for reducing and/or training divers for coping with panic and anxiety occurring underwater.

Hunt J. Psychological aspects of scuba diving injuries: Suggestions for short-term treatment from a psychodynamic perspective.
Journal Clinical Psychology in Medical Settings. 1996; 3: 253-71.

Abstract: Examined psychological reactions to decompression sickness in 3 experienced scuba divers using a psychodynamically-oriented, interview-based approach. These cases are part of a larger study of risk and injury among sport divers ( J. Hunt; 1993, 1995, 1996). Case I (male, aged 29 yrs), Case II (female), and Case III (female, in her 30s) all took diving risks and experienced denial, depression, shame, among other emotions as a result of their errors in judgment. However, their individual reactions also corresponded to other areas of their lives (i.e., familial relationships, occupation, social relationships), which, in turn, affected their reactions to injury. An argument is made that most research studying risk behavior and sports take into account biological, behavioral or cognitive approaches, while ignoring unconscious conflict in risk-taking and injury management.

Hunt J. Diving the wreck: Risk and injury in sport scuba diving.
Psychoanalytic Quarterly. 1996; 65: 591-622.

Abstract: Uses psychoanalytic theory to examine risk and injury in the case of a male deep sea diver. The author examines the unconscious conflicts that appeared to fuel the diver's involvement in deep diving and to lead to a near fatal incident of decompression sickness. Particular attention is paid to the role of the diver's father in the evolution of the preoedipal and oedipal fantasies and conflicts that appear to be linked to the injury. The author's research, which thus far has been based on interviews with and fieldwork among 36 recreational and deep divers, is presented.

Raglin JS, O'Connor PJ, Carlson N, Morgan WP. Responses to underwater exercise in scuba divers differing in trait anxiety.
Undersea & Hyperbaric Medicine. 1996; 23: 77-82.

Abstract: Fifteen male scuba divers performed underwater leg ergometer exercise in an effort to determine if trait anxiety was related to their physiologic or perceptual responses. Psychological assessment completed before exercise testing revealed that the sample exhibited positive psychological profiles. However, five individuals possessed trait anxiety scores above the published mean (M = 46.0). Their responses to exercise were compared with the five participants with the lowest trait anxiety scores (M = 30.6). The exercise task was 20 min of steady-state underwater leg ergometer exercise. Oxygen consumption, CO2 production, minute ventilatory volume, breathing frequency, and heart rate were assessed at rest and every 5 min during exercise. Perception of effort and breathing discomfort were also determined during exercise. Each of the physiologic and perceptual variables increased (P < 0.05) with exercise. The only group main effect (P < 0.05) occurred for respiration rate. The high trait anxious group took 7.4 fewer breaths per minute (13.1 vs. 20.5) compared with low trait anxious group. These results have implications regarding the use of intervention strategies in persons at potential risk of experiencing panic while scuba diving.

Griffiths TJ. The effects of relaxation and cognitive rehearsal on the anxiety levels and performance of SCUBA students.
International Journal of Sport Psychology. 1985; 16: 113-119.

Abstract: 48 undergraduate beginning SCUBA students trained during 1 semester (control) and 63 undergraduate beginning SCUBA students trained during a 2nd semester (relaxation/cognitive rehearsal [RCR]) received similar training with the exception that the RCRs listened, on 3 occasions, to an audiotaped program designed to reduce diver state anxiety and improve underwater performance. Ss completed baseline measures of the State-Trait Anxiety Inventory (STAI) and a stimulus-response inventory of general trait anxiousness. Ss were reassessed on the STAI prior to performance evaluations of the deepwater quarry dive and the bail-out procedure that required Ss to don and remove SCUBA equipment. Results reveal significantly lower levels of state anxiety in the RCRs than in the controls prior to both the bail-out and deepwater quarry dive performances. A significant performance difference between these same groups was found only in the bail-out maneuver, suggesting that RCR must be task specific in order to positively modify performance.

Vaernes RJ. Eidsvik S. Central nervous dysfunctions after near-miss accidents in diving.
Aviation Space & Environmental Medicine. 1982; 53: 803-807.

Abstract: The possible differences in specific central nervous system functions in 2 groups of divers were studied: Divers with a history of diving accidents (accident group, N = 9) and accident-free divers (non-accident group, N = 15). Both groups were characterized with a mean I.Q. level (WAIS) within the normal range. Of the nine accident group divers, 8 showed abnormalities on neuropsychological tests implicating lesions on higher CNS levels. In addition, five of the accident group divers had a syndrome of subcortical/limbic dysfunctions--specific memory deficits, low autonomic reactivity, sustained attention problems, and emotional lability. The data confirmed previous findings that a severe diving accident may lead to cerebral dysfunctions. However, in contrast to the previous studies, our study indicated that divers with average intellectual levels can develop specific CNS dysfunctions after a near miss diving accident. Therefore, we conclude that a combined effect of emboli with multifocal lesions and/or a more specific effect on limbic structures represent the pathophysiology of a severe near-miss diving accident.

Griffiths TJ, Steel DH, Vaccaro P, Karpman MB. The effects of relaxation techniques on anxiety and underwater performance.
International Journal of Sport Psychology. 1981; 12: 176-182.

Abstract: Investigated the effects of 2 relaxation techniques on the levels of self-reported anxiety and physiological stress among SCUBA divers prior to an underwater task. In addition, the effect these relaxation techniques have on actual performance of a difficult underwater task was investigated. 50 college students from a beginning SCUBA class were randomly assigned to either a biofeedback relaxation group, a meditation group, or a control group. Ss were administered the State-Trait Anxiety Inventory, and physiological measures of heart rate, respiration rate, hand temperature, and frontalis muscle action potential were taken before and after relaxation training. Data indicate that differences existed between the 3 groups on measures of state anxiety following relaxation training. Significant correlations were detected between state anxiety and performance and between trait anxiety and performance.

Mears J, Cleary P. Anxiety as a factor in underwater performance.
Ergonomics. 1980; 23: 549-557.

Abstract: 24 male and 8 female experienced (3-30 hrs) scuba divers (average age 23 yrs) were divided in 4 groups, and each group made 1 dive to 6 or 30 m in day or night conditions. Manual dexterity, time estimation, and cognitive performance (Raven's Progressive Matrices) data were obtained on the surface and under water; heart and respiration rates were monitored before and during the dive. Ss completed the State-Trait Anxiety Inventory Scale X-1 before and after the dive. Both anxiety and heart rate decreased under water in the 6-m groups and increased in the 30-m groups, but respiration rates remained elevated throughout. A 14-30% decrease in manual dexterity occurred at 6 m and a 45-47% decrease at 30 m; cognitive performance improved at 6 m but decreased 26-36% at 30 m. There was a 15% decrease in manual dexterity at 6 m in the day and 30% at night; for the 30-m group, decreases of 45 and 47% were found for day and night conditions, respectively. Although time estimation varied greatly on the surface, all Ss tended to overestimate a time standard under water. Results support the notion that anxiety is a contributory factor in performance decrements under water.

Biersner RJ, Ryman DH. Prediction of scuba training performance.
Journal of Applied Psychology. 1974; 59: 519-521.

Abstract: 296 trainees of the US Navy School for Divers Second Class completed a demographic questionnaire, a health inventory, and an attitude survey. Significant multiple correlations in a validation sample and in a cross-validation sample were obtained between these variables and a pass-fail performance criterion. Scales dealing with mental health and training apprehension were the most significant predictors.

Relevant Books:

Dash M. Conquering your fear of water: An innovative self-discovery course in swimming. Bloomington: AuthorHOUSE; 2006.

Piantadosi CA. The biology of human survival: Life and death in extreme environments. Oxford: Oxford University Press; 2003.

Edmonds C, Lowry C, Pennefather J, Walker R. Diving and subaquatic medicine, 4th ed. London: Edward Arnold Publishers; 2002.

Chowdhury B. The last dive: A father and son's fatal descent into the ocean's depths. New York: Harper Collins; 2000.

Nevo B, Breitstein, S. Psychological and behavioral aspects of diving. Flagstaff: Best Publishing; 1999.

Bachrach AJ, Egstrom GH. Stress and performance in diving. San Pedro: Best Publishing; 1987.