Scuba diving is a physiologically demanding activity conducted in an environment that is hostile to human survival without equipment. This is not a reason to avoid it — the equipment works, the training prepares you, and millions of dives are completed safely each year. It is a reason to approach the medical aspects of diving seriously, because the consequences of ignoring them range from inconvenient to fatal.
This guide covers the medical requirements for diving in Australia, the most common health issues that affect divers, and the practical safety planning that every diver should do before any reef trip.
The Diving Medical
In Australia, recreational scuba diving requires a diving medical certificate signed by a physician trained in diving medicine before you can enrol in an open-water certification course. Many dive operations also require a medical clearance from guests who have certain health conditions, regardless of existing certification.
The standard diving medical form used in Australia is the ADAS (Australian Diver Accreditation Scheme) Diving Medical or the equivalent AS/NZS 2299 form. The assessment covers cardiovascular health, respiratory function, ear and sinus health, neurological function, and general fitness. The examination takes approximately 30 to 45 minutes and can be conducted by any general practitioner who has completed the appropriate training, or by a physician with specific diving medicine qualifications (listed by the South Pacific Underwater Medicine Society at spums.org.au).
Absolute contraindications to diving include: active asthma (controlled asthma requires specific assessment — not an automatic disqualification, but requires specialist evaluation), spontaneous pneumothorax history, certain cardiac conditions, active seizure disorders, and some psychiatric medications that affect consciousness or judgment. These are not exhaustive — the full list should be discussed with a physician who understands diving physiology.
Common conditions requiring assessment rather than automatic exclusion: controlled asthma, diabetes (increasingly accepted with appropriate management protocols), controlled hypertension, minor cardiac issues, ear and sinus problems, and a history of decompression sickness.
If you have any chronic health condition, do not assume it prevents diving — seek assessment from a diving medicine specialist rather than a general practitioner who may be unfamiliar with the current evidence on diving with various conditions.
Decompression Sickness (DCS)
Decompression sickness — also called “the bends” — is caused by nitrogen bubbles forming in the body’s tissues when a diver ascends too quickly, not allowing adequate time for dissolved nitrogen to be expelled via normal breathing. The bubbles form in joints, the spinal cord, the brain, the lungs, and other tissues, causing symptoms ranging from joint pain to paralysis to death.
DCS is not an unpredictable event that happens to unlucky divers. It is a predictable consequence of diving profiles that exceed the no-decompression limits established by dive tables and dive computers, or that involve multiple dives that accumulate nitrogen load beyond safe limits.
Prevention: Use a dive computer and stay within its limits. Ascend at the recommended rate (9 metres per minute maximum, slower in the final five metres). Do a three-minute safety stop at five metres on every dive. Avoid repetitive deep dives without adequate surface intervals. Do not fly or ascend to altitude within 12–18 hours of diving (24 hours after decompression dives).
Symptoms: Joint pain, skin mottling, neurological symptoms (numbness, tingling, weakness, confusion), and respiratory distress. Symptoms typically appear within 24 hours of surfacing, most commonly within 6 hours.
Treatment: Recompression in a hyperbaric chamber is the definitive treatment. The nearest hyperbaric facility to the main reef destinations is relevant information every diver should know before a trip:
- Cairns: Cairns Private Hospital has a hyperbaric unit
- Townsville: Townsville University Hospital has a hyperbaric unit
- Whitsundays: Townsville is the nearest facility (approximately 280km from Airlie Beach)
- Exmouth/Ningaloo: Fremantle Hospital in Perth is the nearest major hyperbaric facility; the RFDS can arrange emergency evacuation
DAN (Divers Alert Network) Australia provides 24-hour emergency assistance for diving accidents, diving medical advice, and connects divers with the nearest appropriate hyperbaric facility. DAN membership and dive accident insurance is strongly recommended for all reef divers.
Ear and Sinus Health
The most common medical issue affecting recreational divers is ear-related — specifically, the failure to equalise middle ear pressure on descent.
As a diver descends, the increasing water pressure compresses the air space in the middle ear. Equalisation — the Valsalva manoeuvre (pinching the nose and gently blowing), Toynbee manoeuvre, or the jaw-movement Frenzel technique — opens the Eustachian tube and allows air to flow from the throat into the middle ear, equalising the pressure difference.
Failure to equalise causes pain. Continued descent without equalising causes a middle ear squeeze, which can rupture the eardrum — a serious and painful injury that requires medical treatment and several weeks out of the water to heal.
Preventing ear problems: Never force equalisation. If you can’t equalise at a given depth, ascend one or two metres and try again. Equalise frequently during descent — every metre, not every few metres. Never dive with a head cold, active sinus infection, or significant nasal congestion. Use a decongestant if genuinely necessary, with the caveat that if the decongestant wears off at depth, the resulting pressure differential can cause a reverse squeeze on ascent.
Swimmer’s ear (otitis externa) — infection of the outer ear canal — is a common diver ailment caused by repeated water exposure. Prevent it by thoroughly drying the ear canal after diving (a few drops of diluted isopropyl alcohol can help), avoiding insertion of foreign objects, and treating early infections promptly.
Sun, Heat, and Hydration
Tropical reef travel exposes you to sustained sun intensity in an environment where the water’s surface reflection multiplies UV exposure significantly. Sunburn on a liveaboard is a guaranteed outcome for anyone who doesn’t manage sun exposure carefully.
Use reef-safe sunscreen (mineral-based, zinc oxide or titanium dioxide) and apply it before entering the water, not on the boat. Reapply after each water session. A rash vest or wetsuit is the most effective sun protection for time spent in the water.
Dehydration is a specific risk for divers, who lose fluid through respiration in the dry compressed air of the scuba regulator, through sweat in the wetsuit, and through the general fluid losses of a tropical environment. Drink water consistently throughout the dive day. Avoid alcohol before diving — its diuretic and judgment-impairing effects are both problematic in the diving context.
Heat exhaustion in tropical conditions is a real risk on days with high heat, sun exposure, and physical activity. Symptoms include heavy sweating, weakness, dizziness, and nausea. Rest, shade, and fluid replacement are the immediate response. Heat stroke — in which the body loses the ability to regulate temperature — is a medical emergency.
Travel Vaccinations
For reef travel within Australia, no specific vaccinations are required beyond standard childhood immunisations.
For international reef travel to Papua New Guinea, Indonesia, or the Pacific Islands, the relevant vaccinations and prophylaxis include: Hepatitis A and B, typhoid, malaria prophylaxis (for PNG and parts of Indonesia), and ensuring tetanus and polio are current. The timing of some vaccinations requires advance planning — hepatitis B immunisation series takes several weeks to complete. Consult a travel medicine clinic six weeks before international reef travel departure.
The One Piece of Safety Advice Most Divers Don’t Follow
Always dive with a Surface Marker Buoy (SMB) and deploy it before surfacing. The SMB is an inflatable tube that you inflate at depth and send to the surface before you ascend — it marks your position for the surface boat and makes you visible to other vessels in the area.
On a liveaboard or day-trip vessel with an experienced surface crew, the SMB is a courtesy and a safety backup. In any situation where the boat has lost track of you, or where you surface away from the vessel due to current, the SMB is the difference between a quick pickup and an extended surface search. In open ocean away from a vessel — which happens to experienced divers on drift dives more often than people expect — the SMB is the reason the search boat finds you before dark.
Carry one. Use it every dive. The diver who doesn’t deploy their SMB because “the boat knows where we are” is the diver who creates the most anxiety for the surface crew and the most risk for themselves.
The reef is safe to dive. Your safety planning is what keeps it that way.
