Scuba Diving Fitness: Medical Requirements and Physical Prep
The question I get most often from people considering their first certification isn't about gear or technique. It's: "Can I actually do this?" They have a health history. Medications. A surgery three years ago. A dad who had a heart attack.
The honest answer is: probably yes, but let's make sure.
Diving is not an extreme sport in the athletic sense. But it does place real physiological demands on your body, and some medical conditions interact badly with the underwater environment in ways that are predictable and preventable — if you know about them beforehand.
The RSTC Medical Questionnaire
Every major certification agency (PADI, SSI, NAUI, SDI) uses a standardized medical screening form based on the Recreational Scuba Training Council (RSTC) medical questionnaire. You fill this out before your first confined water session.
The form asks about a long list of conditions and symptoms. If you answer "yes" to any of them, you need a physician sign-off before you can begin training. This is not bureaucratic gatekeeping — it's a meaningful filter that has caught serious issues before they became underwater emergencies.
The form asks about:
- Heart conditions (heart attack, angina, irregular heartbeat, cardiac surgery)
- Lung conditions (asthma, emphysema, spontaneous pneumothorax, chest surgery)
- Neurological conditions (seizures, blackouts, fainting, stroke)
- Ear and sinus problems (chronic ear infections, perforated eardrum, sinus surgery)
- Diabetes
- Pregnancy
- Mental health conditions on medications affecting alertness or judgment
- Recent surgery or hospitalization
- Medications that could affect alertness or cardiovascular function
Conditions That May Prevent Diving
Some conditions represent absolute contraindications. These are rare, but they're worth knowing:
Uncontrolled epilepsy is one. A seizure underwater — even a brief one — is almost certainly fatal. The risk doesn't disappear with controlled epilepsy (most agencies require 5 years seizure-free with medical clearance), but uncontrolled seizures are a hard stop.
Spontaneous pneumothorax (a collapsed lung with no traumatic cause) is another. Even after surgical repair, the risk of recurrence under pressure changes creates enough concern that most dive medicine physicians will advise against recreational scuba.
Severe COPD or emphysema with air trapping creates a lung over-expansion risk on ascent similar to breath-holding — the damaged, non-compliant lung tissue may not allow air to escape normally as ambient pressure decreases.
Uncontrolled heart failure or severe coronary artery disease with recent symptoms are also hard stops. The cardiovascular demands of diving — increased workload, cold stress, exertion — create real risk for cardiac events underwater.
Conditions That Need Clearance (Not Disqualification)
Far more conditions fall into the "needs evaluation" category rather than automatic exclusion. The diving medicine literature has evolved significantly here.
Asthma: Previously considered a near-disqualification, moderate well-controlled asthma is now considered compatible with diving by many dive medicine authorities, with appropriate evaluation. Exercise-induced asthma, however, is higher risk given the exertion demands of diving.
Diabetes: Type 1 and Type 2 diabetics can dive, but management requirements are significant. Hypoglycemia underwater is an emergency. PADI and SSI have specific diabetic diver guidelines covering blood glucose ranges, dive duration limits, and buddy communication protocols.
Heart conditions and cardiac history: A history of heart attack, arrhythmia, or coronary artery disease requires individual evaluation. Key questions are current functional status (can you exercise at moderate intensity?), medication interactions with diving, and whether the underlying condition is stable and controlled.
Ear issues: Chronic perforated eardrums or surgical ear procedures may prevent equalization, which is necessary for every descent. ENT evaluation before certification is standard.
Medications: Sedating antihistamines, certain antidepressants, and other CNS-active medications can impair underwater judgment and should be discussed with a dive medicine physician.
The Divers Alert Network (DAN) maintains an excellent reference library on medical conditions and diving. If you're uncertain, their Medical FAQ is worth reading before your physician appointment.
Physical Fitness for Diving: What's Actually Required
Good news: you don't need to be an athlete. The physical demands of recreational diving in calm conditions are modest — roughly equivalent to a moderate walk or a light swim.
That said, diving can escalate quickly. Surface swims back to the boat against a current, equipment failure drills, helping a struggling buddy — these require bursts of genuine exertion. You want to have some reserve.
What matters:
- Basic swimming ability. Most agencies require you to swim 200 meters (any stroke, no time limit) and float or tread water for 10 minutes. This is genuinely not a high bar.
- Cardiovascular reserve. You should be able to sustain moderate aerobic activity — a brisk walk, light jogging — for at least 20 minutes without stopping. If you can't, that's worth addressing before you start training, not because of certification requirements but because underwater emergencies don't wait for you to catch your breath.
- Strength for equipment. A full scuba setup with tank weighs 20–30 kg. You need to be able to manage it at the surface and on a boat deck. This is about functional movement, not athletic performance.
Age and Diving
Children: PADI's Bubblemaker program starts at age 8, in controlled conditions up to 2 meters. Junior Open Water certification is available at 10 (PADI) and is a real certification with appropriate depth restrictions. At 15, juniors can certify as full adults. The limiting factor with young divers is usually psychological readiness (can they focus and remain calm?) rather than physical capability.
Older adults: There is no upper age limit on diving with medical clearance. Divers in their 70s and 80s dive regularly. The risks that increase with age — cardiovascular disease, reduced lung function, medication interactions — are all addressable through proper medical screening. An annual check-in with a dive medicine physician becomes more important as you age.
FAQ
I had a heart attack 2 years ago. Can I ever dive?
Possibly, yes. The key factors are your current functional status, whether the underlying coronary disease is treated and stable, your exercise tolerance on a stress test, and your current medications. This requires evaluation by a cardiologist familiar with dive medicine — not a general "your heart is fine" clearance. Some post-MI patients return to diving; others don't. DAN has specific guidance on this.
My doctor has no idea about diving medicine. What should I do?
Many general practitioners have little familiarity with diving physiology. DAN maintains a physician referral network of dive medicine-trained physicians. For complex cases, a hyperbaric medicine specialist or a physician affiliated with a hyperbaric center is the best option. Bring the RSTC medical form and be prepared to explain what diving actually entails physiologically.
Do I need to update my medical clearance over time?
Most agencies require an annual medical form update if you answered "yes" to any items on the form. If your health status changes significantly — new diagnosis, surgery, change in medications — you should get re-evaluated before diving, regardless of how long ago your last clearance was.
Can I dive while pregnant?
No. All major training agencies and dive medicine organizations recommend against diving during pregnancy. The risks to the fetus from decompression stress and potential nitrogen bubbles crossing the placenta are not quantified well enough to consider it safe. After delivery, clearance from your OB is appropriate before returning to diving.