Sight Search

How Deep Can We Go?

Text by Dennis Guichard
Understanding the human limits of deep-water saturation diving.

I must be honest and clarify upfront that I’m a total shallow-water diving whimp. I’m not against taking risks if those are adequately calculated and prepared for but I do feel much more comfortable frolicking in the shallows than I do in the depths. I just know that if I have any equipment malfunction that I’m in relatively safe reach of the surface, and the corals & fish life are frequently so much more abundant on the shallower reefs.

I do however have the utmost respect and admiration for the people doing deep water dives and there is unavoidably a part of me, as I’m sure is equally true for many, that is attracted to the deep water perhaps in just conquering all the technical challenges of getting there and back safely.

When most of us think about shallow versus deep diving, our fathoming thereof is limited in conversation to water perhaps shallower than 18m depth, in comparison to the deep-water technical diving that some people are frequently doing closer to 100m depth. But then there are recreational divers also pushing the utopia of that depth concept to the extreme with open-water scuba and closed-circuit rebreathers to over 300m depth. And then again there are commercial saturation divers who are pushing the very boundaries of what seems possible with human limitations currently as deep as 701m depth.

As far back as 1959, diver Hannes Keller became interested in extensive deep diving and started developing tables for mixed gas decompression. Not a diver himself, the now-famed physician Professor Albert Bühlmann became intrigued with the project and got involved helping develop the algorithms and gas mixtures to support that work.
 
Keller successfully tested the new Bühlmann gas mixtures and decompression tables in Lake Zürich where he reached a record water depth of 120m, and then again in Lake Maggiore in Brissago, Switzerland, where he reached a water depth of 220m (1961) with diver Damian McLeish.

Professor Bühlmann was central to much of the early work that made deep water diving possible and many new depth records were established over time by numerous divers using his decompression algorithms: In December 1960 a depth of 250m was achieved in the French Navy chamber in Toulon. In December 1962 a depth of 305m was achieved by Hannes Keller in California with the US Navy. In October 1966 a depth of 220m was achieved off Italy with a Capshell saturation expedition. And in February 1969 a depth of 350m was achieved off the coast of England near Alverstone.

In 1975 a revolutionary new 1,000m capability hyperbaric chamber was opened at the University of Zürich funded personally by Professor Bühlmann, also with the support of Canton of Zürich, the Swiss Confederation, the French Military, and Shell International. In February 1981, dive No 373 reached 575m depth pressure in the Zürich chamber. It was a revolutionary achievement for that early time.

But deep diving isn’t without its risk and challenge - divers face a host of debilitating physiological and psychological challenges when their bodies are subjected to the intense pressures at those limiting depths.

The deep dive record for open-circuit scuba currently stands at a staggering 332.35m depth, set by Ahmed Gabr in the Red Sea in September 2014. The descent to that depth took 15-minutes whilst the ascent took some 13-hours and 35-minutes with all his decompression obligations.
 
Prior to that the depth record had been held by Nuno Gomes with a dive to 318.25m, also in the Red Sea in 2005, although Nuno still holds the record for the deepest cave dive at 282.6m depth (a 339m altitude-adjusted sea level equivalent depth), set in 1996 at Boesmansgat in South Africa. The woman’s deep diving record was also recently broken in Boesmansgat on 27th October 2022 by Karen van den Oever with a dive to 246.65m depth, breaking her own previous record dive to 236.04m depth.

According to Wikipedia there are only 21 recreational/technical divers who have ever descended below a depth of 240m on either open or closed-circuit scuba. The holy grail of open water diving below the 300m limit has reportedly only been achieved six times since John Bennett first broke that barrier in 2001. The deepest dive record of 316m, on a closed-circuit rebreather, was set by Jarek Macedoński in Italy, on 10th October 2018.

Defying all the odds of nitrogen narcosis and central nervous system oxygen toxicity, Dan Manion amazingly set the current record for a deep dive on air at 155m depth. Manion reported he was almost completely incapacitated by nitrogen narcosis and has no recollection of his time at that depth.
 
The list of names of divers who have attempted setting various deep-water records, but died in the process, is sadly an extensive one. The deep is not for the feint hearted.

The realms of ‘properly deep’ diving however belong to the superheroes of commercial diving - the saturation divers. They who can master the deep likewise master a substantial commercial and financial advantage over their competitors and so the race to develop technologies and decompression algorithms bespoke to those challenges has been a fiercely contested one. There are seemingly few organisations who have the capability to do saturation dives to even 300m, so the realms of achieving dive depths deeper than that to perhaps 500m, or up to a 1,000m, are even fewer again.
 
Technology is perhaps the ‘simple’ part, as we already have that available to permit us access to the deepest oceans, with Victor Vescovo achieving a manned-vessel depth of 10,927m at the base of the Mariana Trench in April 2019. Putting humans into the water is however quite another challenge altogether limited it seems by the body’s capability to cope with the immense hydrostatic pressures.

In regular scuba diving we are limited by progressive risk of incapacitating nitrogen narcosis at anything over perhaps 18m depth and limited beyond 30m on air because the exertion of breathing enhanced gas density beyond 5.2g/litre at that depth can trigger an exponential risk of carbon dioxide build-up in the body. Carbon dioxide can also have a narcotic impact on our ability to think clearly as it has a narcotic potential 20-times more than nitrogen, causing increased blood flow to the brain and heightening our risk of severe neurological decompression sickness.
 
n dives below 50m depth, a reduction in endothelial function of the pulmonary arteries commonly occurs. Interestingly the mechanisms were shown to be different between males and females with the dysfunctionality occurring more severely in males from a change in nitric oxide bioavailability, whereas in females there was a resultant imbalance of circulating prostanoid signalling hormones which function to control vasoconstriction and are mediators of inflammatory reactions.

In dives to 60m performed by the Poland Naval Academy in 2021, elevated biomarkers of endothelial dysfunction (ICAM-1 and VCAM-1) were identified. These help regulate inflammation-associated vascular adhesion and the migration of white blood cells to repair endothelial damage.
The endothelium is sensitive to oxidative stress and these biomarkers might be a key measure as a decompression sickness stress marker.
66m depth is of course the maximum recommended depth for dives on air because of the high risk of central nervous system oxygen toxicity convulsions, let alone the severity of nitrogen narcosis at this depth.

In deep technical and commercial diving beyond 50m depth, it is common to dilute the nitrogen component of our breathing gas with a less narcotic inert gas like helium. This permits us to dive deeper with a clearer mind but from around 150m depth helium itself becomes problematic in causing high pressure nervous syndrome (HPNS). HPNS manifests with hyperexcitability, tremors, changes in brain wave electrical activity, alterations in cognitive function, and even convulsions at more extreme depths.
 
Strategies to minimise HPNS include slowing the descent rate on compression, including stage stops to permit diver acclimatisation, limiting excessive oxygen partial pressure, and diluting the helium with other inert gasses like nitrogen or hydrogen, although those equally each have narcotic potency of their own. Diver selection is also key for deep water saturation operations as individual susceptibilities are common and dive teams are often carefully selected by saturation supervisors to suit the dive operation intended.  

Incorporating these dive management adjustments has permitted divers to achieve depths of up to 534.4m (Comex Hydra 8 excursion in 1988) in the Mediterranean Sea, as well as a record simulated depth pressure of 701m in a hyperbaric chamber. However, despite these strategies using various gas mixtures, many exploratory dives have had to be aborted because divers have often experienced psychotic disorders like hallucinations and delirium, which seem to be as a result of the combined various narcotic potencies of the mixed gas solutions. As you solve one problem you invariably create another it seems.
 
In a saturation dive to 273m in July 2017, the deepest performed in Australian waters, many of the dive team reported suffering hallucinations, nausea, tremors, and cognitive impairment, allegedly due to too rapid descent procedures, that seems to have left many with residual injury and which has resulted in legal proceedings against the dive operator by the Commonwealth Director of Public Prosecutions in Australia.  

In dives beyond about 260m it has been seen that divers can also experience ‘nocturia’ where they have sustained diuresis needing to urinate endlessly and thus suffer from disturbed sleep that quickly leads to exhaustion. With dives from about 450m depth, disruption in EEG brain wave activity has been seen as well as disruption of REM sleep and awake cycle periods ultimately leading to diver exhaustion.

In deep saturation dives at 500m depth, a decrease in small airway and diffusion function was shown through a Chinese study, with divers suffering decreased Forced Vital Capacity and Forced Expiratory Volume for up to 3-days post dive, thought to be induced through airway lesions.

On 20th November 1992, Greek diver Theodoros Mavrostomos achieved a chamber dive depth of 701m with the French COMEX Hydra 10 operation, breathing a mixture of Hydrogen/Helium/Oxygen (Hydreliox), after the rest of this team were held incapacitated at 675m depth. The slow controlled descent for that dive took 13-days, the team spent 3-days at 675m depth pressure with a short 2-hour excursion to 701m by Theodoros, and then took just over 23-days of decompression time to get back safely to the surface. A remarkable achievement that hasn’t been matched or surpassed now for 30-years.

Because of the limiting constraints of psychotic-like disorders due to inert gas narcosis at great depth, regardless of the gas mixtures used, it is estimated that the maximum operating depth limit for humans might be in the region of 1,000m depth. Even with the administration of inhalational anaesthetics it is estimated that no human dives would be possible beyond 1,200m depth even in divers showing a low sensitivity to Hydreliox narcosis.

Categories

 2022
immersion and bubble formation 232bar AGE AIDA Accident management Accidents Acid reflux Acute ailments Advanced courses Rescue diver Aerobic exercise After anaesthesia Aged divers Air Quality Air consumption Air exchange centre Air hose failure Air supply Airway control Air Alert Diver December 2022 Alert Diver Magazine Algorithms Alice Cattaneo Alice Modolo Alternate Airsources use Alternater Air Source Alternative gas mix Altitude changes Altitude diving Altitude sickness Aluminium Oxide Ama divers Amino acids Amos Nachoum Anaerobic Metabolism Anilao Animal life Annual renewal Antarctica Anxiety Apea Apex predators Apnea Apnoea Aqua corps Aquatic creatures Aquatic life Aquatics and Scuba Diving Archaeology Argonaut octopus Argonauts Argon Arrythmia Arterial Gas Embolisms Arterial gas embolism Arthroscopic surgery Aspirin Audible signals Aurel hygiene Australian Flat backed Australia Aviation o2 BCD BHP BLS BWARF Baacterial infections Back adjustment Back pain Back treatment Backextensors Backmount CCR Badages Bag valve mask Bahamas Bail out cylinder Balancing Bandaids Barbell back squat Barometric pressure Barotrauma Basic Life Support Basslets Batteries Beach entry Beached coral Becky Kaga Schott Becky Kagan Schott Beluga whales Bench press Bends Benign prostate hyperplasia Benzophenones Beth Neale Beyond Standards Big Sur Bilikiki Tours Biophysics Black Water Photography Black Blood flow Blood pressure Blood thinners Blue Desert Blue Wilderness Blue economy Blue heron Bridge Blurred vision Boat diving Boat safety Bobbit worm Boesmans gat Boesmansgat Bonaire Bone fractures Bouyancy compensators Bouyancy controls Boyle's Law Boyle\'s Law Bradycardia Brain Brandon Cole Breast Cancer Breath Hold Diving Breath hold diver Breath holding Breath hold Breath-hold Breathing Gas Breathing gas contamination Breathing oxygen Breathing Breathold diving Bright Bank Broken bones Bruising Bubble detection Bubbleformation Buddy Exercise Buddy checks Buoyancy Burnshield CCR CE markings 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 Cardiac research Cardiaccompromise Cardio health Cardiological Cardiomyopathy Caribbean Carmel Bay Carribean Conservation Catalina Island Cave diving Cave exploration Caves Cave Cenotes Ceotes Challenging Environments Chamber Safety Chamber science Chamber treatment Charging batteries Charles' Law Charles\' Law Charles\\\' Law Charles\\\\\\\' Law Charles\\\\\\\\\\\\\\\' Law Charlie Warland Chemotherapy Chest compressions Children diving Chiropractic Chlorophll Chokka Run Christina Mittermeier Citizen Conservation Citizen sciences Citizen science Clean Air Cleaning products Climate change Closed Circuit Rebreathers Closed Circuit Rebreather Cmmunity partnership Coastal diving Coastalexcursion Cold Water Cold care Cold sores ColdWater Cold Commercial Fishing Commercial diving Commercial schools Common consideration Common understanding Communication Composition Compressed Air Compressed gas Compressor operators Compressors Concussion Congestive heart Faiture Consercation Conservation Photographer Conservation photography Conservation Contact lenses Contaminants Contaminated air Coping with cold Coral Bleaching event Coral Conservation Coral Reefs Coral Restoration Coral bleaching Coral preservation CoralGroupers Corals Core strength Corona virus Coro Coservation Costamed Chamber Courtactions Cozumel Cradiac valvular Cristina Mittermeier Crohns disease Crowns Crystal build up Crystallizing hoses Cubs Cutaneous decompression Cutting tools Cylinder Ruptures Cylinder capacity Cylinder handwheel Cylinder safety Cylinder valves Cylinder weight Cylinders DAN Courses DAN Europe DAN Profile DAN Researchers DAN medics DAN members DAN report DANTraining DCI DCS Decompressions sickness DCS theories DCS DEMP DM training DNA DReams DSMB Daan verhoeven Dahab Dalton's Law Dalton\'s Law Dalton\\\'s Law Dalton\\\\\\\'s Law Dalton\\\\\\\\\\\\\\\'s Law Danel Wenzel Dangerous Marinelife Dauin island Dave McCowan David Doubilet Dean's Blue Hole Dean\'s Blue Hole Deco dives Decompression Illness Decompression Sickness Decompression Stress Decompression chamber Decompression illsnes Decompression ilness Decompression limits Decompression treatment Decompression Decorator crabs Deep Freediving Deep diving Deep water exploration Deepest SCUBA Dive Delayed Offgassing Dental Depth limits Dever Health Diadema Response Team Diagnosis Diaphragms Diopter Discomfort Diseases Disinfection Disorientation Distraction Dive Buddy Dive Chamber Dive Chmber Dive Computer Dive Destinations Dive Destination Dive H Dive Industry Dive Instruction Dive Instructor Dive Lights Dive Medical Form Dive Medical Dive Practices Dive Professionals Dive Pros Dive Rescue Dive Research Dive Safari Dive Safety Tips Dive South Africa Dive Training Dive Travel Wakatobi Dive Travel Dive accidents Dive buddies Dive caves Dive computers Dive courses Dive cover Dive cylinder Aluminium Dive equipment Dive excursions Dive exercise Dive exeriences Dive experience Dive fitness Dive gear Dive heallth Dive health Dive in Africa Dive insurance Dive medical insurance Dive medicals Dive medicines Dive medicine Dive operators Dive opportunities Dive planning Dive procedures Dive safety 101 Dive safety Dive safe Dive skills Dive staff Dive travels DiveLIVE DiveTravel Diveleader training Diveleaders Diver Food Diver Health Diver Profile Diver Travel Diver education Diver infliencers Diver on surface Diver recall Diverover 50 Divers Alert Diversafety Divesites Diving Divas Diving Family Diving Fatalities Diving Feet Diving Helmets Diving Kids Diving Programs Diving Trauma Diving career Diving emergencies Diving emergency management Diving fit Diving guidelines Diving history Diving injuries Diving science Diving suspended Diving Dizziness Dolphins Domestic Donation Doug Perrine Dowels Dr Rob Schneider Drift diving Drysuit diving Drysuit valves Drysuits Dynamic environment Dyperbaric medicines EAPs EAP EMS EN standards Ear barotrauma Ear pressure Ear wax Ears injuries Eco friendly Ecowise Education Electronic Embolisms Emergency Action Plan Emergency Planning Emergency action planning Emergency decompression Emergency plans Emergency treatments Emergency underwater Oxygen Recompression Emergency Endurance Entry Envenomations Enviromental Protection Environmental factors Environmental impact Environmental managment Environmental stewardship Equalisation Equalization Equipment care Equipment failure Equipment inspection Equipment significance Evacuations Evacuation Evaluations Even Breath Evironmetaly friendly Exercise Exercising Exhaustion Exposure Protection Extended divetime Extinction Extinguisher Extreme treatments Eye injuries FAQ Face computer Factor V Leiden Failures FalseBay Diving Fatigue Faulty equipment Feet Femal diver Female divers Fenivir Fetus development Filling stations Fillings Fin Foot Fins Fire Coral Fire Safety Fire extinguisher Firefighting First Aid Equipment First Aid Kit First Aid Trainig First Aid Training First Aid kits First Aid Fish Identification Fish Life Fish Fit to dive Fitness Levels Fitness Training Fitness evaluation Fitness to dive Fitnesstrainng Fitness Flying Focus lights Food Footissues Foundations Fractures Francesca Diaco Francois Burman Fred Buyle Fredive Free Student cover Free diving Free flow Freedive Competition Rules Freedive Competiton Freedive INstructor Freedive Safety Freedive Training Freedive computer Freedive rescue procedures Freediver Freedive Freediving Instructors Freediving performance Freediving Fur rade Galapagos Gar Waterman Gardens of The Queen Gas Density Gas Planning Gas consumption Gas emboli Gas laws Gas mixes GasPerformance Gasblends Gases Gass bubbles Gastoeusophagus Gastric bypass Gastroenterologist Gas Gear Servicing Germs Geyer Bank Giant Kelp Forest Giant Kelp Giant stride Girls that Scba Gobies Golden fish Gordon Hiles Great White Sharks Green sea turtle Green turles Greenlings Guinness World Record Gutt irritations HBOT HCV HELP HIRA HMLI HMS Britanica Haemorhoid treatment Hand signals Harry Chammas Havanna Hawaii Hawksbill Hazard Description Hazardous Marine life Hazardous marinelife Head injuries Headaches Health practitioner Healthy Food Heart Attack Heart Health Heart Rate monitor Heart fitness Heart rates Heart rate Heart Heat loss Heat stress Heliox Helium Gas Helium Hematoma Hemodynamic Hepatitis C Hepatitus B Hiatal Hernia High Pressure vessels High pressure hoses High temperatures Hip strength Hip surgery Hippocampus History Hole in the heart Hood Hot Humans Hydrate Hydration Hydrogen Hydroids Hydrostatic pressure Hygiene Hyperbaric Chamber Hyperbaric Oxygen Treatments Hyperbaric Oxygen Hyperbaric research Hyperbaric treatment Hyperbarics Hypertension Hypothermia Hypoxia I-52 found INclusivity IdentiFin Imaging Immersion Immine systems In Water Recompression Increased pressure Indemnity form Indian Ocean Indigo SCuba Indonesia Inert gas Infections Infra red Imaging Injections Inner ear Instinct Instruction Instructors Insulation Insurance policy Insurance Integrated Physiology International travel International Internship programs Internship Interval training Irritation Irukandji Syndrome Isotta housing Itchy Rash Its OK Jellyfish Jill Heinerth Joanna Wyrebek Joint pain Journal for Technical Diving Junior Open Water Diver KZN South Coast KZN Karen van den Oever Kate Jonker KateJonker Kenya Kidneys Kids scubadiver Komati Springs KwaZulu Natal LED lights Labour laws Lake Huron Lara Lambiase Laryngospasm Lauren Arthur Learning to dive Leatherbacks Leatherback Legal Network Legal advice Legislation Lembeh Straights Lenses Leslie Lwaney Leukemis Liability Risks Liability releases Liability Life expectancy Lifestyle Lighting Lightroom editing Lionfish Live aboard diving Liveaboard Liver Toxicity Liver diseas Liz Louw Loss of consciousness Lost at sea Low Visability Low blood pressure Low pressure deterioration Low volume masks Lumpsuckers Lung Irritation Lung flexibility Lung function Lung injuries Lung squeeze Lung surgery Lung MOD MOzambique diving MPA Macro photography Mafia Island Maintenance Malaria Mammalian Dive Response Mammalian effect Manatees Mandarin Fish Marfan syndrome Marine Biologist Marine Biology Marine Mega fauna Marine Science Marine Scientists Marine conservation Marine parks Marine plants Marinelife Marinescience Markus Dirschi Marlin Marne protecte areas Mask clearing Masks Master scuba diver Matty Smith Maximum operating depth Medical Q Medical emergencies Medical oxygen Medical questionaire Medical statement Medical team Medicalresearch Medicalstudents Medication Mehgan Heaney-Grier Membership benefits Menopause Menstruation Mermaid Danii Mesophotic Metotrexate Mexico Michael Aw Micro Photography Microbubbles Middle ear pressure Mike Bartick Military front press Misool Resort Raja Ampat Mixed Gas Mono Fins Mooring lines More pressure Motion sickness Motionsickness Mount Kilimanjaro Mozambique Muck Diving Muscle pain Mycobacterium marinum NDL limits Narcosis National Geographic Nature Nausea Nautilus Ndibranchs Neck pain Neoprene layers Neuro assessments Neurocognitive research Neurological assessments Neuromotor exercises New Caledonia Nichola Bird Nicorette Nicotine Nitrogen Narcosis Nitrogen build up Nitrox No Decompression Limits No-decompression limits No-decompression Non-nano zinc oxide Non-rebreather Mask Non-smoking Nondiving related illness Nonrebreather masks Normal Air North Sulawesi Nosebleeds Nudibranchs Nuno Gomes Nutrition O2 enriched O2 oxygen provider. O2 providers O2 servicing O2treatments OOxygen maintenance Ocean Projects Ocean Research Ocean animals Ocean conservation Ocean mammals Ocean migrations Ocean pollution Oceangate Octopus Oil contamination Olive Ridley Open Ocean Open water divers Optical focus Oral contraseptives Orbital implants Oronasal mask Osteonecrosis Otters 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 kit Oxygen masks Oxygen providers Oxygen supplies Oxygen supply Oxygen systems Oxygen therapy Oxygen treatment Oxygen P J Prinsloo PADI Freedivers PFI PFO PJP Tech Paper Nautilus Paralysis Parentalsupervision Part 3 Partner Training Patent foramen ovale Pemba Island Peri-peri Divers Perspective Peter Lindholm Philippine Islands Philippines Phillipines Photographers Photographer Photography tips Photography Physical Fitness Physioball Physiology Physiotherapy Pills Pilot Whale Pistons Planning Plastic Plimsoll Interface Pneumonia Pneumothorax Poison Polka Dot Bat fish Pollution Pool Diving Pool chemicals Pool maintenance Pool workout Pools Post-dive Potuguese man-of-war Pre-dive Predive check Pregnancy Pregnant divers Preparation Prepared diver Press Release Preventions ProDive Port Elizabeth Professional rights Protection Provider course Psycological Pulmanologist Pulmonary Barotrauma Pulmonary Bleb Pulmonary Edema Pulmonary Hypertension Pulse Punture wounds Pure Air Pure Apnea Purge Quit Smoking Q RAID South Africa RCAP REEF RMV Radio communications Range of motion Rashes Rebreather diving Rebreatherdive Rechargeable batteries. Recompression chamber Recompression treatment Recompression Recycle Red SEA Reef Chcek Reef Conservation Reef Environmental Education Foundation Reef protection Reef safe Reef surveyors Refractive correction Regal Sea Goddesses Regulator failure Regulators Regulator Remote areas Remote islands Renewable Report incidents Rescue Divers Rescue Procedure Rescue breathing Rescue breaths Rescue diver Rescue skills Rescue skill Rescue training Rescue Research Respitory Minute Volume Resume diving Return To Diving Return to diving Reuseable items Risk Assessments Risk assesments Risk assessment Risk elements Risk management Risks of Seizures Riviera Maya Roatan Marine Park Roatan SABS 019 SAC SMB SRC SafariLive Safe diving practices Safety Concerns Safety Gear Safety Stop Safety in Air Safety SaherSafe Barrier Salish Seas Salty Wanderer Sanitising Sanne Volja Sara Andreotti Sara Banderby Sara Campbell Sardine Run Sargassum sea Saturation Diving Save our seas Schrimps Science Scoliosis Scombroid Poisoning Scorpion Fish Scuba Air Quality Scuba Guru Scuba Injury Scuba Instructor Scuba children Scuba divers Scuba dive Scuba education Scuba health Scubalearners Scubalife Sea Horses Sea Turtles Sea slugs Seagrass Sealcolonies Sealife Seals Seasickness Seaweeds Seaweed Sea Self Rescue Shallow Water Blackout Shallow dives Shark Protection Shark Research Shark conservation Shark diving Sharks Shipwrecks Shit Happens Shore entries Shoulder strength Sidemount Sideplank Signs and Symptoms Silty bottoms Sit-ups Sixgill Sharks Skills in action Skin Bends Skin outbreak Skin rash Smart phone photography Snells Window Snorkeling Snorkels Social Distancing Sodwana Bay Solomon Islands Sonnier bank South Africa Southern Sea Otters SpareAir Sperm Whales Spinal Bend Spinal bends Spinal cord DCS Spinal dura Spinal pain Spinner dolphins Spleen Splits Sports medicine Squeezes Squid Run Stability exercise Stage cylinder Standars Statin Mediction Stay Fit Stay Warm Steel Stefan Randig Stents Step ups Stephen Frink Stepping up Stockton Rush Stonetown Stretch band exercise Stretch bands Strobe Lighting Strobes Stroke Submerge tech Submerged Sudafed Sulawesi Sun protection Sun screen Sunscreen Supplemental oxygen Surface Air Consumption Surface Consumption Rate Surface Marker Buoys Surface supplied Air Surfaced Surgeries Surgery Suspension training Swim Fitness Swimmers health SwimmingIn wateractivities Swimming Sylvia Earl Symbiosis Symbiosys TRavel safety Tabata protocol Talya Davidoff Tanzania Tattoes Tec Clark Tech diving Technical Diving Technical divng Temperature Homeostatis The Bends The Cavettes The Titanic Wreck The Wild Coast The greatest Shoal The silent world The truth Thermal Notions Thermoregulation Thomas Peschak Thunder Bay National Marine Sanctuary Tides Tips and trick Tonga Tooth squeeze Transplants Travel destinations Travel smarter Travel tips Travel Tropical Coastal Management Tulamben Tullum Tulum. Tunnelling Turks and Caicos Turtles Tweezers Ultrsound Umkomaas Unconscious diver Unconsciousness Underground waterways Underground work Underseaa world Underwaater Photos Underwater Photography Underwater Photograper Underwater Photograpgraphy Underwater Photographer Manirelife Underwater Research Underwater camera Underwater critters Underwater floral Gardens Underwater hockey Underwater imaging Underwater photographer Underwater photography Underwater photos Underwater pho Underwater sound Underwatercommunications Underwater University of Stellenbosch Unresponsive Urchins Urinary retention. VGE Vacations Vaccines Vagus nerve Valsalva manoeuvers Valve stem seals Vape Vaping Vasopressors Vasvagal Syncope Venous gas emboli Ventilate Venting Verna van Schak Veterinarian Videography Vincenzo Ferri. 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 Whitetpped Sharks Wide Angle Photos Wide angles Wildlife park Wildlife Winter Wits Underwater Club Wolf Eels Woman and diving Woman in diving Womans health Woman Women In Diving SA Women and Diving Women in Freediving Women in diving Womens Month Womens health Work of Breathing Workout World Deeepst Dive Record World Records Wound dressings Wreck History Wreck divers Wreck dive Wreck diving Wreck exploration Wreckdiving Wrecks Yoga Youth diver Zandile Ndholvu Zanzibar Zoology Zooplankton \ Blennies 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 biodiversity bloodcells blue carbon body art breathing air calories burn canal blockage carbon dioxide toxicity cardiovascular career developments cerebrospinal fluid cervical spine checklist chemo port children child chronic obstructive pulmonary disease clearances closed circuit scuba compressed gass coral growth corrective lenses currents cuts cylinder filling dead lift decompression algorithms decongestants decongestion deep dive training dehydration discovery dive clubs dive injuries dive medicing dive ready child dive reflex dive tribe divecomputers diver in distress diver rescue diver training dive diving attraction diving hoods doctors dolphns 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 fish watching fitness Balance fitnes flexible tubing frediving freedivers gas bubble gas poisoning gastric acid gene expression health heartburn histidine hospital humidity hypobaric hypoxia immersion and bubble formation immersion pulmonary edema (IPE informal education isopropyl alcohol jaundice join DAN knee lanyard laparoscopic surgery life jackets longevity lower stress lox oxygen level lungs malaise mamalian effect marielife marine pathogens medical issues medical procedures medical risk assesment medications mental challenge mental preparedness micro-organisims micro minor illness mucous membranes multilineage dysplasia myelodysplasia nasal steroids nasal near drowning nematocysts neurological newdivers nitrogen bubbles no tanx off-gassed operating theatre operations orthopeadic otitis media out planting outgas pain parameters perforation phillippines phrenic nerve physical challenges pinched nerves plasters pneumoperitoneum polyester-TPU polyether-TPU post dive posture prescription mask preserve prevention professional emergency responders proper equalization psychoactive pulmonary barotrauma. pulmonary injury. pulmunary barotrauma pure oxygen radiation rebreather mask rebreathers retinal detachment risk areas safety stops saturation scissors scuba equipment scuba sea goddesses single use sinus infections situationalawarenes smoking snorkeling. spearfishing sterilising stings strength sub-aquatic sunscreen lotion swimmers ears tattoo care tecnical diver thermal protection tissue damage toxicity trachea training trimix unified standards upwelling virtual coach vision impaired vomiting warmers water quality zinc oxide