Sight Search

Scuba Diving and Life Expectancy

By Peter Buzzacott, MPH, Ph.D.

A study of 2,872 pairs of Danish twins concluded that only about 25 percent of life expectancy is attributable to genetics; the other 75 percent is likely due to lifestyle factors.

(1) Twenty years after this was published in 1996, a study sponsored by National Geographic identified five places in the world where, per capita, people reach 100 years old 10 times more frequently than they do in the United States.

(2) A team of researchers visited those five places to investigate what lifestyle factors might explain this remarkable longevity; while there, they interviewed 263 centenarians. They found these common factors: leading an active lifestyle, applying mechanisms for lowering stress, having a sense of purpose and belonging to the right tribe (a group of people who share similar interests).

In addition to the factors that are common among the world's oldest residents, many other factors might add a few years to our life expectancy. For example, in 2013 the American Heart Association published a statement that concluded owning a dog probably decreases the risk of cardiovascular disease.3 All this research made us wonder how recreational scuba diving affects life expectancy. We asked the experts.

Diving burns more calories than many people think. It is a very gentle form of exercise, but it is exercise nonetheless. Given that the diving population is aging steadily, do you think this type of cardiovascular exercise might be beneficial for divers, on average, or could the added cardiovascular stress be potentially harmful?

Ingrid Eftedal, Ph.D.: Diving is associated with environmental factors that affect the cardiovascular system, and as long as the total amount of physiological stress is limited and the diver is reasonably fit, no data indicate that diving is harmful to the cardiovascular system. In addition to the health-promoting effects of exercise, one may speculate that diving could have additional benefits for the heart. It has been known for some time that breathing high amounts of oxygen activates an important type of proteins known as molecular chaperones (for historical reasons they are sometimes called heat shock proteins). Some of these molecular chaperones directly protect the heart from injury; extra oxygen is sometimes administered to patients before heart surgery for this reason.

Dawn Kernagis, Ph.D.: Scuba diving can be a fantastic way to burn calories, with a recreational dive burning an estimated 300 to 600 calories per hour depending on temperature and activity level. Although most recreational diving can be very relaxing while still involving increased activity and low levels of joint stress, which is beneficial to individual health, some forms of diving can be strenuous and could put an individual with predisposing conditions at potential risk of injury or incident. It's important to remember that physical fitness is a major factor in determining potential risk with any form of increased physical activity, so risk associated with increased activity will largely depend on a diver's overall physical condition.

When divers breathe air or nitrox at depth, reactive oxygen species are produced. Otherwise known as free radicals, these molecules have been found to be negatively associated with diseases and aging. On the other hand, regular exposure to low levels of oxidative stress might lead to immune responses that are similar to acclimatization. Do you think exposing ourselves to oxidative stress builds resilience in divers or has undesirable consequences?

Kernagis: As with most biological systems, there is an optimal balance with respect to the degree of oxidative stress we are exposed to. Scuba diving can lead to a state of increased oxidative stress in which increased production of free radicals occurs not only due to increased physical activity but also due to the changes in the environmental conditions underwater (e.g., exposure to heat or cold, breathing high-pressure oxygen, being in a high-pressure environment). The combined influence of these diving-related factors on free radical production and the long-term effects on diver resilience and health have yet to be studied in depth but will be important in future research.

Eftedal: Environmentally imposed stress — oxidative stress in particular — is a hot topic in research. Oxidative stress is a double-edged sword. Current knowledge indicates that our cells need a certain quantity of free radicals for biological signal transduction. When the production of free radicals exceeds the body's antioxidant capacity, however, the radicals may harm cell membranes, proteins and DNA, advancing cell aging processes and potentially causing gene mutations that may lead to diseases such as cancer. There is a vital balance, and the immune system appears to be involved in maintaining it. Still, there is nothing to indicate that safe diving destroys the balance between good and bad oxidative stress.

Compared with nondivers who are the same age, same gender and live in the same state, divers are thought to be just as likely to have high blood pressure and/or high cholesterol but less likely to smoke or be obese. Having children is known to increase life expectancy (maybe because the kids can look after their aging parents), but active divers are thought to be 25 percent less likely to have children. On the other hand, divers are much more likely than nondivers to visit a doctor each year. With regard to these lifestyle factors, how do you think divers might fare in the long run compared with nondivers?

Eftedal: I believe that healthy lifestyle choices, careful diving among them, are likely to lead to lower frequency of disease in the long run. Choosing activities you enjoy makes life more interesting, whether or not it is longer.

Kernagis: The factors listed previously, in addition to numerous additional factors — including alcohol consumption, sleep quality, environmental exposures, fitness and nutrition — will have varying impacts on long-term health and wellness. Genetics will also play a role in how these factors interplay and ultimately affect a diver's health. Generalizing about nondivers versus divers is difficult. An individual who doesn't dive might be active in another way that has positive influential factors on his or her overall lifestyle. A healthy diver who is relatively active, doesn't smoke and follows a balanced diet, however, will have lower risks for certain diseases and injuries that could decrease quality of life or overall lifespan for others.

Compared with the rest of the population, divers are traditionally thought to have, on average, higher levels of education and higher incomes. This might translate into better nutrition, safer cars and fewer poor health decisions. On the other hand, it might mean faster cars and greater indulgence. How likely is it that better education and higher earnings over the lifespan might affect longevity?

Kernagis: Previous research has frequently pointed to a correlation between increased lifespans and improved education or higher income. A recent study emphasized that, between these two factors, higher education is a better predictor of longer lifespan.4 The study determined that more education can lead to improved cognitive abilities, which lead to better choices for health- and wellness-driving behaviors. The link between health and income is likely due to the influence of education status on earnings: Better education is often correlated with a higher income.

Eftedal: To my knowledge, better education is a predictor of higher life expectancy on its own. From there, it becomes hard to discern factors on the levels of causation versus association (e.g., higher earnings tend to follow education). One additional factor — improved gender balance with women moving into traditionally male-dominated fields — may make a positive difference for risk management.

Some recreational dives may produce bubbles that cause no symptoms, and bubbles have been linked to endothelial damage (damage to the lining of our blood vessels). Could bubbles be good for us by cleaning plaque out of our blood vessels or regularly renewing the lining? Or are they probably all bad news for divers?

Eftedal: Intravascular bubbles are interesting; they appear so frequently in diving yet only occasionally cause injury or disease. I am not convinced that bubbles have anatomy on their side for acting as pipe cleaners though. Vascular damage, including atherosclerotic plaque, typically occurs in arteries, whereas decompression-induced bubbles are usually found in veins, where the blood pressure is lower. What we observe will always depend on the tools we use, however, and when it comes to bubbles I am sure there is much left to explore — good and bad.

Kernagis: While numerous studies have demonstrated transient endothelial dysfunction because of vascular bubbles, we have not extensively studied potential beneficial effects of bubbles passing through our blood vessels.

When subjected to environmental stresses, humans respond through genetic up or down regulation. Is it possible that regular divers have greater resilience to other environmental stresses because they dive? What about greater resistance to diseases such as cancer?

Kernagis: Diving exposures, in addition to other exposures such as exercise, can precondition individuals for protection in subsequent dives. It has been suggested that this preconditioning could also increase resilience in other environmental extremes, such as hypoxia or environmental stressors that affect the immune system, but more studies need to be conducted to fully assess this potential effect of diving.

Eftedal: Yes, there are genetic data that indicate that regular divers may develop resilience. Along with Croatian researchers, we compared experienced technical divers to nondivers a few years ago. We found that the divers had specific genetic activity changes in their blood cells compared with the nondivers and that these changes might counteract negative effects of oxidative stress. Although diving may promote resilience on a basal biological level, however, we cannot say whether this affects cancer risk. Published data on cancer mainly concerns professional divers who may also have been exposed to chemical pollutants at work, which puts them in a different category than sport and recreational divers.

Recent research suggests that recreational diving is relatively safe, with around two deaths per million scuba dives.5 Despite that, drowning is the most common cause of death in recreational diving. How might a relatively small risk of accidental drowning affect the average life expectancy of divers?

Eftedal: Although drowning is a risk not to be taken lightly, I believe that the health benefits of physical exercise in general, including diving, are more likely to affect life expectancy of divers as a group.

Kernagis: Given the extremely low mortality rate in recreational diving, I don't believe the risk of accidental drowning will have a significant impact on the average life expectancy of divers overall. Divers can minimize their risk of accidental drowning or other types of dive accidents even further, however, by following safe diving practices.

Finally, if we were to conduct a twins study and follow thousands of pairs of twins where one twin scuba dives and the other does not, do you think we might see a difference in life expectancy?

Eftedal: This would be a dream design for research: the perfectly controlled study. If I were to gamble, my bet would be that even with the risks involved in diving, you would find a higher number of centenarians among the diving twins because of acquired acclimatization against environmentally imposed stress.

: To truly assess the impact of diving on life expectancy, each pair of twins would need to live an otherwise equivalent lifestyle. Factors that are known influences on longevity such as nutrition, physical activity, environmental exposure and psychological stress would have to be the same for both twins from birth.

1. Herskind AM, McGue M, Holm NV, Sorensen TI, Harvald B, Vaupel JW. The heritability of human longevity: a population-based study of 2872 Danish twin pairs born 1870-1900. Human Genetics 1996; 97(3):319-23.
2. Buettner D, Skemp S. Blue Zones: Lessons from the world's longest lived. American Journal of Lifestyle Medicine. 2016; 10(5):318-21.
3. Levine GN, Allen K, Braun LT, Christian HE, Friedmann E, Taubert KA, et al. Pet ownership and cardiovascular risk: a scientific statement from the American Heart Association. Circulation 2013 June 11; 127(23):2353-63.
4. Lutz W, Kebede E. Education and health: redrawing the Preston curve. Population and Development Review 2018; 44(2):343-61.
5. Buzzacott P, Schiller D, Crain J, Denoble PJ. Epidemiology of morbidity and mortality in US and Canadian recreational scuba diving. Public Health 2018; 155:62-68.

Meet the Experts
Ingrid Eftedal, Ph.D., is a researcher and project manager in the Department of Circulation and Medical Imaging at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. She is a civil engineer with expertise in biophysics and medical technology; her Ph.D. is in molecular biology. Eftedal's work focuses on how the body reacts and acclimatizes to the diving environment.

Dawn Kernagis, Ph.D., is a research scientist at the Florida Institute for Human and Machine Cognition, where she specializes in human performance optimization and risk mitigation. She has a biochemistry degree from North Carolina State University and a Ph.D. from Duke University, where she studied gene array-based diagnostic development in the settings of undersea medicine and cancer.

© Alert Diver — Q3 Summer 2018


Aqua Pool Noodle ExercisesUnderwater Photographer and DAN Member Madelein Wolfaardt10 Simple Things You Can Do to Improve Your Underwater PhotographyCOVID-19 and Diving: March 2021 UpdateDiver Return After COVID-19 Infection (DRACO): A Longitudinal AssessmentGuidelines for Lifelong Medical Fitness to DiveExperienceFitness Myth or Fitness Fact?The Safety of Sports for Athletes With Implantable Cardioverter-DefibrillatorsCardiovascular Fitness and DivingHypertensionPatent Foramen Ovale (PFO)Headaches and DivingMiddle-Ear Barotrauma (MEBT)O’Neill Grading SystemMask Squeeze (Facial Barotrauma)Sinus BarotraumaInner-Ear Barotrauma (IEBT)Middle-Ear EqualisationAlternobaric VertigoDecompression IllnessOn-Site Neurological ExaminationTreating Decompression Sickness (The Bends)Top 5 Factors That Increase Your Risk of the BendsHow to Avoid Rapid Ascents and Arterial Gas EmbolismUnintended Rapid Ascent Due to Uncontrolled InflationUnexpected Weight LossFlying After DivingWisdom Tooth Extraction and DivingYour Lungs and DivingScuba Diving and DiabetesDiving after COVID-19: What We Know TodaySwimmer’s Ear (Otitis Externa)Motion SicknessFitness for DivingDiving After Bariatric SurgeryWhen to Consult a Health-Care Provider Before Engaging in Physical ActivitiesFinding Your FitnessHealth Concerns for Divers Over 50Risk Factors For Heart DiseaseJuggling Physical Exercise and DivingSeasickness Prevention and TreatmentMember to Member: Guidelines for SeniorsHigh-Pressure OphthalmologyOver-the-Counter Medications
immersion and bubble formation Accidents Acid reflux Acute ailments After anaesthesia Air Quality Air exchange centre Air hose failure Air supply Airway control Air Alert Diver Magazine Alternative gas mix Altitude changes Altitude diving Altitude sickness Aluminium Oxide Ama divers Amino acids Anaerobic Metabolism Animal life Annual renewal Apnea Apnoea Aquatic life Aquatics and Scuba Diving Archaeology Arterial Gas Embolisms Arterial gas embolism Arthroscopic surgery Aspirin Aurel hygiene BCD BHP BLS BWARF Back adjustment Back pain Back treatment Backextensors Badages Bag valve mask Bahamas Balancing Bandaids Barbell back squat Barometric pressure Barotrauma Basic Life Support Batteries Becky Kagan Schott Bench press Benign prostate hyperplasia Benzophenones Beth Neale Beyond Standards Bilikiki Tours Biophysics Black Blood flow Blood thinners Blue Wilderness Blue economy Blurred vision Boat safety Boesmans gat Boesmansgat Bone fractures Bouyancy compensators Boyle's Law Boyle\'s Law Bradycardia Brain Breast Cancer Breath Hold Diving Breath holding Breath hold Breath-hold Breathing Gas Breathing gas contamination Breathing Breathold diving Bright Bank Broken bones Bruising Bubbleformation Buddy Exercise Buddy checks Buoyancy Burnshield CGASA CMAS CO2 COVID-19 Updates COVID-19 COVID CPR Cabin pressure Caissons diseas California Camera equipment Camera settings Cameras Cancer Remission Cancer treatments Cancer Cannabis and diving Cannabis Cape Town Dive Festival Cape Town Dive Sites Cape Town CapeTown Carbon Monoxide Carbon dioxide Cardio health Cardiological Cardiomyopathy Caribbean Carmel Bay Catalina Island Cave diving Challenging Environments Chamber Safety Chamber science Charging batteries Charles' Law Charles\' Law Charles\\\' Law Charles\\\\\\\' Law Charles\\\\\\\\\\\\\\\' Law Charlie Warland Chemotherapy Chest compressions Children diving Chiropractic Chlorophll Christina Mittermeier Citizen Conservation Cleaning products Closed Circuit Rebreathers Cmmunity partnership Coastalexcursion Cold Water Cold care ColdWater Cold Commercial Fishing Commercial diving Commercial schools Composition Compressed Air Compressed gas Consercation Conservation Photographer Conservation photography Conservation Contact lenses Contaminants Contaminated air Coral Conservation Coral Reefs Coral Restoration Coral bleaching CoralGroupers Corals Core strength Corona virus Coro Costamed Chamber Courtactions Cozumel Cristina Mittermeier Crohns disease Crowns Crystal build up Crystallizing hoses Cutaneous decompression Cylinder Ruptures Cylinder handwheel Cylinder valves DAN Courses DAN Profile DAN Researchers DAN medics DAN members DAN report DCI DCS Decompressions sickness DCS theories DCS DEMP DM training DNA DReams Dalton's Law Dalton\'s Law Dalton\\\'s Law Dalton\\\\\\\'s Law Dalton\\\\\\\\\\\\\\\'s Law Danel Wenzel Dangerous Marinelife Dauin island Dean's Blue Hole Dean\'s Blue Hole Deco dives Decompression Illness Decompression Sickness Decompression Stress Decompression illsnes Decompression treatment Decompression Decorator crabs Deep diving Deep water exploration Deepest SCUBA Dive Delayed Offgassing Dental Dever Health Diaphragms Diopter Diseases Disinfection Dive Buddy Dive Chamber Dive Computer Dive Destinations Dive H Dive Industry Dive Instruction Dive Instructor Dive Medical Form Dive Medical Dive Practices Dive Pros Dive Research Dive Safety Tips Dive South Africa Dive Training Dive Travel Wakatobi Dive Travel Dive accidents Dive buddies Dive computers Dive courses Dive excursions Dive exercise Dive experience Dive fitness Dive gear Dive heallth Dive health Dive medicals Dive medicines Dive medicine Dive operators Dive planning Dive procedures Dive safety 101 Dive safety Dive safe Dive skills Dive staff Dive travels DiveLIVE Diveleader training Diveleaders Diver Health Diver Profile Diver infliencers Diver on surface Divers Alert Divesites Diving Divas Diving Kids Diving Programs Diving Trauma Diving career Diving emergencies Diving emergency management Diving fit Diving guidelines Diving injuries Diving suspended Diving Dizziness Dolphins Domestic Donation Dowels Dr Rob Schneider Drift diving Drysuit diving Drysuit valves Drysuits Dyperbaric medicines EAPs EAP Ear pressure Ear wax Ears injuries Eco friendly Education Electronic Emergency action planning Emergency decompression Emergency plans Emergency underwater Oxygen Recompression Emergency Enviromental Protection Environmental factors Environmental impact Environmental managment Equalisation Equipment care Equipment failure Equipment inspection Evacuations Evacuation Evaluations Even Breath Exercise Exhaustion Exposure Protection Extended divetime Extinguisher Extreme treatments Eye injuries FAQ Factor V Leiden Failures FalseBay Diving Fatigue Faulty equipment Female divers Fetus development Fillings Fire Coral Fire Safety Firefighting First Aid Equipment First Aid Kit First Aid Training First Aid kits Fish Identification Fish Life Fish Fit to dive Fitness Training Fitness to dive Fitnesstrainng Fitness Flying Focus lights Foundations Fractures Francesca Diaco Francois Burman Fredive Free Student cover Free diving Free flow Freedive INstructor Freedive Training Freediver Freediving Instructors Freediving performance Freediving Gar Waterman Gas Density Gas consumption Gas laws Gas mixes GasPerformance Gases Gass bubbles Gastoeusophagus Gastric bypass Gastroenterologist Gear Servicing Germs Geyer Bank Giant Kelp Forest Giant Kelp Gobies Gordon Hiles Great White Sharks Guinness World Record Gutt irritations HCV HELP HIRA HMLI HMS Britanica Haemorhoid treatment Hazard Description Hazardous Marine life Hazardous marinelife Health practitioner Heart Attack Heart Health Heart Rate monitor Heart fitness Heart rates Heart rate Heart Heat stress Helium Hepatitis C Hepatitus B Hiatal Hernia High Pressure vessels High temperatures Hip strength Hip surgery Hippocampus History Hot Humans Hydrate Hydration Hydrogen Hydroids Hydrostatic pressure Hygiene Hyperbaric Chamber Hyperbaric research Hyperbarics Hypothermia Hypoxia I-52 found INclusivity IdentiFin Imaging Immersion Immine systems In Water Recompression Indemnity form Indian Ocean Indonesia Inert gas Infections Infra red Imaging Injections Inner ear Instinct Instruction Instructors Insurance Integrated Physiology International travel International Interval training Irritation Irukandji Syndrome Isotta housing Joint pain Junior Open Water Diver KZN South Coast Karen van den Oever Kate Jonker KateJonker Kidneys Kids scubadiver Komati Springs KwaZulu Natal Labour laws Lake Huron Laryngospasm Lauren Arthur Learning to dive Legal Network Legal advice Legislation Lembeh Straights Lenses Leukemis Liability Risks Liability releases Liability Life expectancy Lifestyle Lightroom editing Live aboard diving Liver Toxicity Liver diseas Liz Louw Lost at sea Low blood pressure Low pressure deterioration Low volume masks Lung Irritation Lung function Lung injuries Lung squeeze Lung surgery Lung MOD Macro photography Maintenance Malaria Mammalian Dive Response Mammalian effect Mandarin Fish Marine Biology Marine Science Marine Scientists Marine conservation Marine parks Marinelife Masks Master scuba diver Maximum operating depth Medical Q Medical emergencies Medical questionaire Medical statement Medicalresearch Medication Mehgan Heaney-Grier Mermaid Danii Mesophotic Michael Aw Middle ear pressure Mike Bartick Military front press Misool Resort Raja Ampat Mixed Gas Mono Fins Mooring lines More pressure Motion sickness Mozambique Muscle pain Mycobacterium marinum National Geographic Nausea Nautilus Ndibranchs Neck pain Neoprene layers Neuro assessments Neurological assessments Nitrogen Narcosis Nitrogen build up Nitrox No-decompression Non-nano zinc oxide Non-rebreather Mask Nonrebreather masks Normal Air North Sulawesi Nosebleeds Nuno Gomes O2 providers O2 servicing OOxygen maintenance Ocean Projects Ocean Research Ocean pollution Oil contamination Open water divers Optical focus Orbital implants Oronasal mask Osteonecrosis Out and about Out of air Outer ears Outreach Overhead Envirenments Oxygen Administration Oxygen Cylinder Oxygen Units Oxygen deficit Oxygen deicit Oxygen dificiency Oxygen ears Oxygen equipment Oxygen masks Oxygen supplies Oxygen supply Oxygen systems Oxygen therapy Oxygen P J Prinsloo PADI Freedivers PFI PJP Tech Parentalsupervision Part 3 Partner Training Perspective Philippine Islands Philippines Phillipines Photographers Photography tips Photography Physical Fitness Physioball Physiology Physiotherapy Pills Pistons Planning Plastic Pneumonia Pneumothorax Poison Pollution Pool Diving Pool workout Post-dive Pre-dive Predive check Pregnancy Pregnant divers Preparation Prepared diver Press Release Preventions Professional rights Provider course Psycological Pulmanologist Pulmonary Barotrauma Pulmonary Bleb Pulmonary Edema Pulse Punture wounds Pure Apnea Purge RAID South Africa RCAP REEF Radio communications Range of motion Rashes Rebreather diving Rebreatherdive Rechargeable batteries. Recompression chamber Recompression treatment Recompression Recycle Reef Chcek Reef Conservation Reef safe Reef surveyors Refractive correction Regulator failure Regulators Regulator Remote areas Renewable Report incidents Rescue Divers Rescue Procedure Rescue breathing Rescue breaths Rescue training Rescue Resume diving Return To Diving Return to diving Risk Assessments Risk assesments Risk assessment Risk elements Risk management Roatan Marine Park Roatan SABS 019 SMB SafariLive Safety Gear Safety Stop Safety SaherSafe Barrier Salty Wanderer Sanitising Sara Andreotti Sardine Run Saturation Diving Save our seas Schrimps Science Scombroid Poisoning Scuba Air Quality Scuba Guru Scuba Injury Scuba Instructor Scuba children Scuba dive Scuba education Scuba health Scubalearners Scubalife Sea Horses Sea slugs Sealife Sea Shallow dives Shark Protection Shark Research Shark conservation Shark diving Sharks Shipwrecks Shoulder strength Sideplank Signs and Symptoms Sit-ups Skin Bends Skin outbreak Skin rash Snorkeling Snorkels Social Distancing Sodwana Bay Solomon Islands Sonnier bank South Africa Spinal bends Spinal cord DCS Spinal pain Splits Squeezes Squid Run Stability exercise Standars Stay Fit Stents Step ups Stephen Frink Stepping up Strobe Lighting Stroke Submerge tech Submerged Sudafed Sulawesi Sun protection Sunscreen Supplemental oxygen Surface Marker Buoys Surface supplied Air Surfaced Surgeries Surgery Suspension training Symbiosis TRavel safety Tabata protocol Talya Davidoff Tattoes Tec Clark Technical Diving Technical divng The Bends The greatest Shoal The truth Thermal Notions Thunder Bay National Marine Sanctuary Tides Tips and trick Tooth squeeze Transplants Travel smarter Travel tips Travel Tropical Coastal Management Tunnelling Tweezers Ultrsound Umkomaas Unconsciousness Underground work Underseaa world Underwaater Photos Underwater floral Gardens Underwater hockey Underwater photographer Underwater photography Underwater pho Underwater University of Stellenbosch Urinary retention. Vaccines Vagus nerve Valsalva manoeuvers Valve stem seals Vape Vaping Vasopressors Vasvagal Syncope Venting Verna van Schak Virus infections Volatile fuels WWII wrecks War stories Washout treatments Wastewater Watchman device Water Resistance Water Weakness Weigang Xu Weights West Papua Western Cape Diving Wet Lenses Wet diving bell Wetsuit fitting Wetsuites Wetsuits White balance Wide Angle Photos Wide angles Wildlife Winter Wits Underwater Club Woman in diving Womans health Woman Women In Diving SA Women and Diving Women in diving Womens health Work of Breathing Workout World Deeepst Dive Record World Records Wound dressings Wreck divers Wreck dive Wreck diving Wreckdiving Wrecks Yoga Youth diver Zandile Ndholvu Zoology abrasion absolute pressure acoustic neuroma excision adverse seas air-cushioned alert diver altitude alveolar walls anemia antibiotics anticoagulants antiseptics bandages barodontalgia bent-over barbell rows bioassays body art breathing air calories burn carbon dioxide toxicity cardiovascular cerebrospinal fluid cervical spine checklist chemo port children child chronic obstructive pulmonary disease clearances closed circuit scuba corrective lenses currents cuts dead lift decompression algorithms decongestants decongestion dehydration dive injuries dive medicing dive ready child dive reflex dive tribe diver in distress diver rescue diver training dive diving attraction doctors domestic travel dri-suits drowning dry mucous membranes dry suits dry e-cigarettes ear spaces elearning electrolyte imbalance electroytes emergency action plans emergency assessment emergency training environmentally friendly equalising equalizing exposure injuries eyes fEMAL DIVERS fire rescue fitnes flexible tubing frediving freedivers gas bubble gas poisoning gastric acid gene expression health heartburn histidine hospital humidity immersion and bubble formation immersion pulmonary edema (IPE informal education isopropyl alcohol jaundice join DAN knee laparoscopic surgery longevity lower stress malaise marielife marine pathogens medical issues medical procedures medical risk assesment medications mental challenge mental preparedness micro-organisims micro minor illness mucous membranes nasal steroids nasal near drowning nematocysts neurological newdivers nitrogen bubbles off-gassed operating theatre operations orthopeadic otitis media outgas pain perforation phillippines phrenic nerve physical challenges pinched nerves plasters pneumoperitoneum polyester-TPU polyether-TPU post dive posture prescription mask preserve prevention proper equalization psychoactive pulmonary barotrauma. pulmonary injury. pulmunary barotrauma radiation rebreather mask rebreathers retinal detachment risk areas safety stops saturation scissors scuba equipment scuba single use sinus infections smoking snorkeling. spearfishing sterilising stings strength sub-aquatic sunscreen lotion swimmers ears tattoo care tecnical diver thermal protection tissue damage toxicity training trimix unified standards upwelling vision impaired warmers water quality zinc oxide