Behavioral health is a critical aspect of evaluating diver candidates. Unlike physical fitness, psychological readiness can be subtle and is not always apparent in a clinic. For this reason, both medical assessment and observation during training by the diving instructor are essential.

Cognitive and Learning Requirements
Candidates must be capable of understanding and applying diving theory and procedures. Significant intellectual impairment or inability to learn independently is incompatible with safe diving.

Motivation and Behavioral Traits
Responsibility, focus, and the ability to remain calm under stress are essential. Candidates who are easily distracted, panic-prone, or unmotivated should be discouraged from diving.

Psychiatric History
A past history of psychiatric illness does not automatically disqualify a candidate. What matters most is the current psychological state and whether it may impact safe diving. Candidates with major depression, bipolar disorder, psychosis, or current substance abuse should not dive.

Medications
Psychotropic medications can pose risks underwater. Some may cause drowsiness, impaired concentration, or lower seizure threshold, while research on interactions with diving pressures is limited. Candidates stable off medication may be considered individually, preferably with input from a diving medicine physician.

Mild Depression and SSRIs
Mild mood disturbances treated with SSRIs are common and often compatible with diving. Safe diving is more likely if:

• The condition was mild before treatment
• Symptoms are well controlled with medication
• The medication has been used for at least one month without side effects
• The candidate is fully informed of the potential risks

For advanced diving beyond recreational limits, or the use of specialty gases, consultation with a diving medicine specialist is recommended.

Other Psychiatric Medications
Candidates using SNRIs, TCAs, MAOIs, or atypical antidepressants (e.g., bupropion) require case-by-case evaluation due to potential effects on alertness and seizure threshold.

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Scuba diving places extra demands on the heart. Immersion increases the volume of blood returning to the heart, and peripheral blood vessels constrict, raising blood pressure. These changes often occur alongside sustained mild to moderate physical activity. It’s not surprising that cardiac events account for nearly 30% of recreational diving fatalities.

The purpose of cardiovascular screening for divers is to:

• Identify individuals at risk of heart attacks, heart failure, or dangerous arrhythmias underwater
• Ensure the diver has sufficient exercise capacity to handle the physical demands of diving

Certain heart conditions may make diving unsafe, including:

• Untreated coronary artery disease with symptoms
• Stress, dilated, or obstructive cardiomyopathy
• Congestive heart failure
• Moderate or severe pulmonary hypertension
• Long QT syndrome or other arrhythmia-prone channelopathies
• Paroxysmal arrhythmias causing fainting or limiting exercise
• Reduced exercise capacity due to heart disease
• Moderate to severe valve problems
• Complex congenital heart defects
• Atrial septal defects (ASD)
• Implanted cardiac defibrillators

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Divers should not have gastrointestinal conditions that increase the risk of:

• Vomiting or reflux
• Bleeding or perforation
• Diarrhea or abdominal pain

Why it matters:

• Trapped gas from surgery or anatomical changes can expand during ascent, potentially causing pain, rupture, or vomiting.
• Vomiting underwater is extremely dangerous and may lead to drowning.
• Diving often occurs far from medical help, so the risk of sudden GI problems must be carefully considered.

Safe diving requires a healthy gastrointestinal system and awareness of any underlying conditions that could flare up during a dive.

Neurological conditions must be carefully evaluated because they can significantly affect diver safety.

Key considerations:

• Risk of unconsciousness: Any neurological abnormality that could cause a loss of consciousness increases the risk of drowning.
• Spinal cord or brain abnormalities: Conditions that impair perfusion may increase susceptibility to decompression sickness.
• Spinal cord or peripheral nerve issues: Reduced spinal cord reserve may limit recovery if spinal decompression sickness occurs.
• Fluctuating neurological conditions (e.g., migraines with aura or demyelinating diseases) may mimic decompression sickness, making diving unsafe.
• History of head injury with unconsciousness should be assessed for seizure risk.

Blood disorders can affect diving safety in several ways:

• Conditions that alter blood flow or clotting may increase the risk of decompression sickness (DCS).
• Bleeding disorders can worsen ear or sinus barotrauma and make injuries from inner ear or spinal DCS more severe.
• Spontaneous joint bleeding (e.g., in hemophilia) can be confused with decompression illness, complicating diagnosis.
• Thrombophilic disorders (inherited or acquired) may increase the risk of blood clots and susceptibility to DCS.

Hormonal and metabolic conditions can affect a diver’s ability to handle exercise and environmental stress underwater.

Key considerations:

• Obesity may increase the risk of decompression sickness, reduce exercise tolerance, and is a risk factor for coronary artery disease.
• Diabetes with insulin or certain oral medications: Hypoglycemia can cause loss of consciousness, which is extremely dangerous underwater. Diving is generally not recommended unless following established diabetes-specific diving guidelines.
• Pregnancy: Decompression-related bubbles can harm the fetus.

Additional reading: https://dan.org/health-medicine/health-resources/diseases-conditions/cardiovascular-fitness-and-diving/

The eyes and visual system are sensitive to pressure changes and other diving-related stressors. Proper eye function is essential for safety underwater.

Key considerations:

Facemask barotrauma:

• Air trapped in the mask can create negative pressure on descent, causing swelling, bruising, or subconjunctival hemorrhage.
• Severe cases may result in bleeding inside the eye, double vision, or orbital injury.

Intraocular gas:

• Divers with gas bubbles inside the eye (from surgery or trauma) are at high risk of barotrauma.

Decompression-related eye effects:

• Decompression sickness and arterial gas embolism can affect the eyes, causing optic nerve damage, vision loss, double vision, blind spots, or eye muscle pain.

Post-eye surgery considerations:

• Allow full healing before diving.
• Full-thickness corneal surgery, glaucoma procedures, or orbital implants carry additional risks from pressure changes or infection.
• Water exposure to unhealed eye tissues can cause serious infections, including vision-threatening intraocular infections.

Good mobility in and out of the water is essential for safe diving. Divers must be able to:

• Enter and exit the water safely from shore or a boat
• Swim and maneuver underwater effectively
• Handle dive equipment, which can weigh 30 kg (66 lb) or more

Key considerations:

• Reduced mobility, especially on boats or in heavy gear, can increase the risk of accidents.
• Orthopedic conditions that limit exercise performance or underwater movement may make diving unsafe.
• Cases such as amputations or other disabilities should be assessed individually by a physician experienced in diving medicine.

Safe diving requires proper pressure equalization between the water and the:

• External ear canal
• Middle ear
• Paranasal sinuses

Key considerations:

• Failure to equalize can cause pain, injury, or even rupture of air-filled spaces, with potentially serious consequences.
• The inner ear is fluid-filled and non-compressible, but the round and oval windows are sensitive to pressure changes. Previously ruptured windows may be at risk of reinjury during forceful equalization.
• The airway must be clear: the larynx, pharynx, and epiglottis must function normally to prevent aspiration.
• Jaw and facial function must allow proper use of a scuba regulator.
• Individuals with mid-face fractures may be more susceptible to barotrauma or rupture of air-filled cavities.