Diving into the blue to discover another world is paradise for new and experienced divers.  Many share a passion for exploring the reefs, wrecks and unique underwater locations across the world.  But it’s important to ensure you are medically fit and understand how the unique underwater environment can challenge or impact the body through the following changes:

  • Physically through pressure, temperature, noise and light
  • Physiologically through the effects of pressure, decompression illness, barotraumas, gas toxicity, drowning or due to overall medical fitness
  • Psychologically the experience, training, competence or behaviour may cause an impact
  • Some changes might be task or environmentally related such as marine animal encounters, vessel movements, sense of entrapment, currents or visibility

A pre-existing medical condition such as a cardiac condition, respiratory illness or injury, or conditions that may result in a loss of consciousness (eg epilepsy or diabetes) can lead to serious incidents when snorkelling or diving. Understanding your medical fitness when taking part in diving or snorkelling activities will ensure you enjoy a successful dive or snorkel. If you are planning to dive you must notify your travel insurer as it may impact the cost of your policy.

Medical requirements for recreational diving

Resort or introductory diving

An introductory dive is usually offered to those wishing to try a dive for the first time, without the expense of becoming certified. It’s a great way to ensure diving is an activity you would actually like to pursue.  Introductory divers must complete a medical declaration provided by your instructor. The declaration will be used to assess if you are reasonably fit to dive. If a medical condition is acknowledged on the declaration, further medical advice will need to be sought.

Entry level or recreational diving certificate

If you are enrolling in a ‘learn to dive’ course to obtain an entry-level recreational diving certificate, you will be required to complete a self-assessed medical declaration form prior to commencing the course. Apart from declaring any medical issues, potential divers must also advise if:

  • they are over 45
  • have a body mass index over 30
  • they have a waist circumference greater than 102 cm for males and 88 cm for females 

If any of these conditions apply or there are any positive answers to medical questions, participants will be required to provide a dive medical certificate performed by a doctor with experience in dive medicals, to certify they are medically fit to dive.  Divers must also be at least 12 years old and require parent’s permission up to the age of 18 years.

Medical requirements for commercial diving

A commercial diver must hold a current certificate of medical fitness no greater than 12 months old, issued by a qualified medical practitioner, with training and experience in providing underwater medicine for commercial dive medicals. The certificate must be kept for 12 months after the diving work is completed.

Diving injuries and illnesses to avoid

It’s important to eliminate or minimise risk as much as possible when diving.  As mentioned above, there are some illnesses that automatically prevent diving as an activity and it’s important to seek medical advice.  The non-respirable environment can impact the body causing problems such as the following:

Decompression illness

Occurs when an excessive amount of nitrogen in the body starts to form bubbles in blood vessels and tissues as the diver ascends. There is a higher risk if longer time periods are spent underwater, the dive was at depth or if the ascent at the end of the dive is too fast. The bubbles can obstruct blood flow to vital organs or cause serious tissue damage.  If you suspect you have decompression illness immediate hyperbaric oxygen therapy would be required.

Symptoms include:

  • Mental dullness
  • weakness
  • headache
  • dizziness and nausea
  • pins and needles
  • numbness
  • fatigue
  • pains in joints and muscle

Nitrogen Narcosis

Nitrogen narcosis acts like a drug, affecting individuals differently and is caused from breathing nitrogen under pressure usually at depth. Normally recreational divers are restricted to a 30m depth. It can affect a diver’s reasoning, memory, judgement, coordination and concentration. In some cases it can cause panic or anxiety or even lead to an over confidence in a diver with natural or normal survival instincts suppressed.

If a diver exhibits signs of nitrogen narcosis a safe ascent will help to mitigate the symptoms. The following factors may increase the effects of nitrogen narcosis including: poor visibility, excess carbon dioxide, fatigue or heavy work, anxiety or inexperience, the diver feeling cold, alcohol or use of drugs.

Contaminated air

Carbon monoxide or oil contaminants in the air supply can be disastrous for divers.  Contaminated air causes a range of injuries and illnesses including loss of consciousness, convulsions or even death.  Air must contain oxygen and nitrogen only, in the right proportions.

Hypoxic blackout

Often occurring with snorkelers who hold their breath for extended periods of time, oxygen levels drop below a critical level causing hypoxia and a sudden loss of consciousness followed by a ‘blackout’. Snorkelers, especially those experiencing snorkelling for the first time, should be advised about Hypoxic Blackouts to avoid the risk.


A common contributor of diving and snorkelling deaths, panic can reduce a person’s capacity to think rationally and result in diving accidents. Equipment problems, personal factors such as physical unfitness or medical related issues, inadequate training or environmental problems can cause a diver or snorkeler to panic. Adequate and effective training prior to diving or snorkelling can help minimise this issue.

Medical conditions

Existing medical conditions such as cardiac conditions, respiratory illnesses or conditions that can lead to a loss of consciousness such as epilepsy or diabetes, may become worse when diving or snorkelling. Many diving and snorkelling incidents are caused by existing medical conditions and participants need to know the risks and be adequately trained before taking part.


Whenever a person becomes incapacitated in the water, drowning may result. This could be from fatigue, through illness or injury, or from panic. It’s important to ensure you are medically fit to take part in a dive or snorkel, ensure you have the right equipment and receive adequate training and supervision or possess the experience needed to participate.


Caused by the pressure differences that change the volume in air spaces within the body, Barotrauma can cause damage to wherever air pockets are held in the body such as the ears, lungs, sinuses or face-mask cavity. External pressure may become greater than the pressure within the body and if a diver doesn’t equalise their ears on descent or ascent they can perforate their eardrum as a result.

When a diver ascends, the external pressure may become less than the pressure found within the body’s air spaces. For example, if a diver doesn’t exhale on ascent or makes a rapid ascent without exhaling properly to release pressure, their lungs may expand with gas causing lung tissue to be overstretched or tear. Sometimes gas may escape into the bloodstream and could potentially result in a stroke, neurological conditions or even death.

The best way to ensure you are ready for the challenge?

Visit your doctor to make sure you are medically fit to enjoy snorkelling or diving. Many of our doctors are registered as South Pacific Underwater Medicine Society (SPUMS) members and are qualified to perform your assessment. Contact us to find out where you can find an experienced dive doctor by calling 1300 658 844.

WorkSafe - Medical Fitness for Diving