Sight Search

Diving Under the Influence

Recreational scuba diving is enjoyable and it is meant to be so. However, there is a fine line between fun-seeking and hedonism and without an essential sense of responsibility and an awareness of the risks, diving can easily succumb to a culture of pleasure‑seeking and self‑indulgence.

Diving, just like driving, demands a clear mind and technical proficiency at all times. For the same reason, diving under the influence of alcohol or other intoxicating substances is decidedly unwise – both for the diver and for their dive buddies. So, here is a post-festive season reality check on finning under the fruits of fermentation and other intoxicating substances.

It is common knowledge that alcohol impairs one’s ability to perform various mental tasks. Reaction time, visual tracking, concentration, performance of simultaneous tasks, judgement and psychomotor ability are all reduced following the consumption of alcohol [1].
One would not expect any trained diver to deliberately dive while drunk, yet diving the morning after drinking the previous night may still mean that the diver is under the influence with an appreciable blood alcohol concentration (BAC). The liver has only a finite and individual-dependent capacity to metabolise alcohol. So, while the diver may not believe that he or she is impaired, the reality may be different.

A study conducted on recreational divers doing shallow entry dives found significantly greater diving performance impairments with a BAC above 0.04% [2]. These impairments were captured on video-tape and were confirmed by standard “dry” sobriety tests. This is not unexpected considering that cognitive impairment, including functions related to attention and concentration, can be reliably measured when the BAC is 0.02% and above [3]. Perhaps more concerning, however, is that the divers in this study were not aware of their performance impairments or of the increased risk of injury possible from diving while under the influence of alcohol.

A review of over 150 studies on the effects of alcohol on cognitive performance found a number of observations that have direct relevance to the scuba diver [4]. These include:
  • The ingestion of even small amounts of alcohol impairs performance – these effects are noticeable even after one drink.
  • The clearance of alcohol from the blood, at the predictable rate of about 0.015% per hour, does not necessarily equate to improved cognitive performance in the same time.
  • Increased reaction time and decreased co-ordination follow a dose/response curve. In essence, the more alcohol that is consumed, the more impaired these functions are.
  • Persons who have been drinking alcohol consistently underestimate its deleterious effects on their performance.
  • Alcohol affects multiple attention tasks (like scuba diving) to a greater degree than those tasks requiring a single focus of concentration.
In addition to impaired neurocognitive function, alcohol in excess results in a number of physiological changes that can endanger a diver. Acute alcohol intoxication can cause cardiac rhythm disturbances and can impair the heart’s ability to pump. Both are significant concerns even without the added problems of exercise or the underwater environment. Also, alcohol can directly increase the risk of diving accidents. Dehydration, a common consequence of alcohol excess, is a well-known risk factor for decompression sickness (DCS). Alcohol increases heat loss, by dilating blood vessels, which can lead to a diver suffering from hypothermia. Divers suffering from the effects of alcohol over-indulgence are also more likely to be nauseous and vomit during a dive; this not only ruins the dive, but can cause dehydration, impaired attention and an increased risk of a rapid uncontrolled ascent – all of which are known risk-factors for diving accidents.

Lastly, in common with the two drugs also discussed in this article, alcohol can also make the diagnosis of diving medical problems trickier. While underwater, the soporific effects of acute alcohol intoxication are indistinguishable from the signs of nitrogen narcosis. However, upon surfacing, the common manifestations of alcohol intoxication, including inco-ordination, sleepiness, nausea and a headache may either mimic or mask the signs of DCS and so delay its diagnosis and its early treatment or these may result in unnecessary medical interventions being taken. 

According to research conducted by the Diving Diseases Research Centre (now known as DDRC Healthcare), 22% of divers admitted to using one or more illicit drug(s) since learning how to dive and 21% of these divers admitted to using a Class A drug, for example cocaine, or a Class B drug, for example cannabis, between five minutes and six hours before a dive [5].

Cocaine is a stimulant, with effects that are apparent within five minutes of use and generally last for one to two hours, although the late phase effects can endure for a few days following a binge [5]. In simple terms, the acute effects of cocaine can be harmful to the diver in two ways: Firstly, the effects on the central nervous system include mood elevation, impaired judgement and increased risk-taking behaviour. As discussed above, these effects are incompatible with safe diving. Secondly, the stimulation of the cardiovascular system increases the heart rate, blood pressure and the occurrence of abnormal heart rhythms. In the presence of increased physical exertion, these effects have been proven to be risk factors for sudden cardiac arrest.
Cannabis appears to be the drug of choice amongst divers [5]. The behavioural and physiological effects of cannabis commence within 10 minutes of use and, of significance to divers, can last for up to three to five hours [5]. These effects can significantly increase the risk of diving accidents. As with alcohol, cannabis causes altered perception, relaxes inhibitions, impairs judgement and causes mood changes, which can all be compounded by the effects of nitrogen narcosis. Cannabis also causes vasodilatation of blood vessels, increasing the risk of hypothermia, and decreased motor co-ordination, impeding the ability to perform technical tasks. Smoking cannabis or tobacco increases the levels of carbon monoxide bound to haemoglobin in the blood, thereby reducing the body’s ability to transport oxygen by up to 10% [6]. This can reduce the diver’s capacity for exertion and so impair his or her physical ability to respond to an emergency.

In addition to the acute effects of cannabis, long-term exposure can also present problems for the scuba diver. As with smoking cigarettes, chronic exposure to cannabis can cause respiratory problems like chronic bronchitis and sinusitis, which increase the risk of barotrauma and its potentially lethal consequences.

It is worth bearing in mind that the possession or use of Class A and B substances is illegal. Beyond the obvious threat of a criminal charge, the diver needs to consider how his or her medical funder might respond if such substance is thought to have played a role in the cause of a diving accident. It is not inconceivable that the payment for hospitalisation or recompression therapy may be refused.
So, although this advice may seem conservative or even prudish and at odds with the fun-seeking culture of diving, divers should steer clear of using drugs and rather avoid or certainly minimise alcohol intake during diving trips. The alternative is to put yourself and your dive buddy at significant risk of harm
  2. Perrine, M.W., Mundt, J.C. & Weiner, R.I. When alcohol and water don’t mix: diving under the influence. J Stud. Alcohol and Drugs; 1994; 55: p517-524.
  3. Koelega, H.S. Alcohol and vigilance performance: review.Psychopharmacology;  1995; 118: p233–249.
  4. Egstrom, G.H. Effects of alcohol consumption on aquatic performance. E&A News; 1996; 3: p2.
  6. 37 SM10c.pdf

Download Article >

Listen to the audio Podcast >

No Comments


immersion and bubble formation Accidents Acid reflux Acute ailments After anaesthesia Air Quality Air exchange centre Air hose failure Airway control Air Alert Diver Magazine Alternative gas mix Altitude changes Altitude sickness Aluminium Oxide Ama divers Amino acids Anaerobic Metabolism Annual renewal Apnea Apnoea Archaeology 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 Bench press Benign prostate hyperplasia Beth Neale Black Blood flow Blood thinners Blue Wilderness Blurred vision Boat safety 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 Broken bones Bruising Bubbleformation Buddy Exercise Buddy checks Buoyancy Burnshield CGASA CMAS CO2 COVID-19 COVID CPR Cabin pressure Caissons diseas Camera settings Cancer Remission Cancer treatments Cancer Cannabis and diving Cannabis Cape Town Dive Festival Cape Town CapeTown Carbon Monoxide Carbon dioxide Cardio health Cardiological Cardiomyopathy Chamber Safety Chamber science Charging batteries Charles' Law Charles\' Law Charles\\\' Law Charles\\\\\\\' Law Charles\\\\\\\\\\\\\\\' Law Charlie Warland Chemotherapy Chest compressions Chiropractic Chlorophll Citizen Conservation Cleaning products Coastalexcursion Cold Water Cold care ColdWater Cold Commercial diving Commercial schools Compressed Air Compressed gas Consercation Conservation Contaminants Contaminated air Coral Conservation Coral Reefs Coral bleaching Corals Core strength Corona virus Courtactions Crohns disease Crowns Crystal build up Crystallizing hoses Cutaneous decompression 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 Dauin island Dean's Blue Hole Deco dives Decompression Illness Decompression Sickness Decompression Stress Decompression illsnes Decompression treatment Decompression Deep diving Deep water exploration Delayed Offgassing Dental Diaphragms Diseases Dive Chamber Dive Computer Dive Destinations Dive H Dive Industry Dive Instruction Dive Instructor Dive Medical Form Dive Medical Dive Pros Dive Research Dive South Africa Dive Training Dive Travel Dive accidents Dive buddies Dive computers Dive excursions Dive fitness Dive gear Dive heallth Dive health Dive medicines Dive medicine Dive operators Dive planning Dive safety Dive safe Dive staff DiveLIVE Diveleader training Diveleaders Diver Health Diver Profile Diver infliencers Diver on surface Divers Alert Diving Divas Diving Kids 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 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 Evacuations Evacuation Evaluations Even Breath Exercise Exhaustion Extended divetime Extinguisher Extreme treatments Eye injuries FAQ Factor V Leiden Failures Fatigue Faulty equipment Female divers Fillings Fire Coral Fire Safety Firefighting First Aid Equipment First Aid Kit First Aid Training First Aid kits Fish Identification Fish Fitness Training Fitness to dive Fitness Flying Fractures Francois Burman Fredive Free Student cover Free diving Free flow Freedive INstructor Freedive Training Freediver Freediving performance Freediving Gas Density Gas consumption Gas laws Gas mixes GasPerformance Gases Gastoeusophagus Gastric bypass Gastroenterologist Gear Servicing Gordon Hiles Great White Sharks Gutt irritations HCV HELP HIRA HMS Britanica Haemorhoid treatment Hazard Description Hazardous Marine life Hazardous marinelife Health practitioner Heart Attack Heart Health Heart Rate monitor Heart rates Heart rate Heart Heat stress Helium Hepatitis C Hepatitus B High temperatures Hip strength Hip surgery Hippocampus History Hot Humans Hydrate Hydration Hydrogen Hydroids Hydrostatic pressure Hyperbaric Chamber Hyperbaric research Hyperbarics Hypothermia Hypoxia IdentiFin Immersion Immine systems In Water Recompression Indemnity form Indian Ocean Indonesia Inert gas Infections Infra red Imaging Injections Instinct Instruction Instructors Insurance Integrated Physiology International travel International Interval training Irritation Joint pain Junior Open Water Diver KZN South Coast Kidneys Kids scubadiver KwaZulu Natal Labour laws Laryngospasm Lauren Arthur Learning to dive Legal advice Legislation Leukemis Liability Risks Liability releases Liability Life expectancy Lifestyle Lightroom editing Live aboard diving Liver Toxicity Liver diseas Low blood pressure Low pressure deterioration Low volume masks Lung Irritation Lung function Lung injuries Lung squeeze Lung surgery Lung MOD Maintenance Malaria Mammalian Dive Response Mammalian effect Marine Biology Marine Scientists Marine conservation Marine parks Marinelife Masks Master scuba diver Maximum operating depth Medical Q Medical emergencies Medical questionaire Medical statement Medication Mehgan Heaney-Grier Mermaid Danii Mesophotic Middle ear pressure Mike Bartick Military front press Mixed Gas Mono Fins Mooring lines More pressure Motion sickness Mozambique Muscle pain Mycobacterium marinum Nausea Nautilus Neck pain Neurological assessments Nitrogen Narcosis Nitrogen build up Nitrox No-decompression Non-rebreather Mask Normal Air Nosebleeds O2 providers O2 servicing OOxygen maintenance Ocean Research Ocean pollution Oil contamination Open water divers Orbital implants Oronasal mask Osteonecrosis Out and about Outreach Oxygen Cylinder Oxygen Units Oxygen deficit Oxygen deicit Oxygen dificiency Oxygen ears Oxygen equipment Oxygen masks Oxygen supply Oxygen therapy Oxygen P J Prinsloo PFI PJP Tech Part 3 Partner Training Philippine Islands Philippines Phillipines Photography Physioball Physiology Physiotherapy Pills Pistons Planning Plastic Pneumonia Pneumothorax Poison Pollution Pool Diving Post-dive Pre-dive Predive check Preparation Prepared diver Press Release Professional rights Provider course Psycological Pulmanologist Pulmonary Bleb Pulmonary Edema Pulse Punture wounds Pure Apnea Purge RAID South Africa RCAP REEF Radio communications Range of motion Rashes Rebreather diving Rechargeable batteries. Recompression chamber Recompression treatment Recompression Recycle Reef Conservation Reef surveyors Regulator failure Regulators Regulator Remote areas Renewable Report incidents Rescue Procedure Rescue breathing Rescue breaths Rescue training Rescue Resume diving Return to diving Risk Assessments Risk assesments Risk assessment Risk elements Risk management SABS 019 SafariLive Safety Stop Safety SaherSafe Barrier Salty Wanderer Sanitising Sara Andreotti Saturation Diving Save our seas Science Scombroid Poisoning Scuba Air Quality Scuba Injury Scuba Instructor Scuba children Scuba dive Scuba health Scubalearners Sea Horses Sealife Shark Protection Shark Research Shark conservation Shark diving Sharks Shoulder strength Sideplank Signs and Symptoms Sit-ups Skin Bends Skin outbreak Skin rash Snorkeling Snorkels Social Distancing Sodwana Bay Solomon Islands South Africa Spinal pain Splits Squeezes Stability exercise Standars Stay Fit Stents Step ups Stepping up Stroke Submerged Sudafed Sulawesi Supplemental oxygen Surface supplied Air Surfaced Surgeries Surgery Suspension training TRavel safety Tabata protocol Talya Davidoff Tattoes Technical Diving The Bends The truth Thermal Notions Tides Tips and trick Tooth squeeze Transplants Travel smarter Travel tips Travel Tropical Coastal Management Tunnelling Tweezers Ultrsound Umkomaas Unconsciousness Underground work Underwater hockey Underwater photographer Underwater photography Underwater pho University of Stellenbosch Urinary retention. Vaccines Vagus nerve Valsalva manoeuvers Vape Vaping Vasopressors Vasvagal Syncope Venting Virus infections Volatile fuels Washout treatments Wastewater Watchman device Water Resistance Water Weakness Weigang Xu Weights West Papua Wet diving bell Wetsuit fitting Wetsuits White balance Wide angles Winter Woman in diving Woman Women In Diving SA Women in diving Work of Breathing Workout Wound dressings Wreck divers Wreck dive Wreckdiving Wrecks Yoga Youth diver Zandile Ndholvu Zoology abrasion acoustic neuroma excision air-cushioned alert diver altitude anemia antibiotics anticoagulants antiseptics bandages barodontalgia bent-over barbell rows bioassays body art breathing air calories burn carbon dioxide toxicity cardiovascular cerebrospinal fluid checklist chemo port child clearances closed circuit scuba 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 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 jaundice join DAN knee longevity lower stress malaise marine pathogens medical issues medical procedures medical risk assesment medications mental challenge micro-organisims minor illness mucous membranes nasal steroids nasal near drowning nematocysts neurological newdivers nitrogen bubbles off-gassed operating theatre operations orthopeadic outgas pain perforation phillippines physical challenges pinched nerves plasters polyester-TPU polyether-TPU post dive posture preserve prevention psychoactive pulmunary barotrauma 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 swimmers ears tattoo care tecnical diver thermal protection toxicity training trimix unified standards vision impaired warmers water quality