The Intersection of Cannabis (Majiuna) Use and Scuba Diving:

The Intersection of Cannabis (Majiuna) Use and Scuba Diving: A Risky Dive Below the Surface

As recreational cannabis (commonly referred to in some cultures as "majiuna")

becomes increasingly legal and socially accepted, its use in conjunction with physically demanding and potentially hazardous activities like scuba diving is gaining attention. While cannabis is often associated with relaxation and euphoria, its pharmacological effects can pose serious risks when combined with the complex physiological demands of diving. This blog explores the physiological and neurological effects of tetrahydrocannabinol (THC)—the primary psychoactive component of cannabis—on the body and mind, and how these effects intersect dangerously with the underwater environment. We also review the potential for increased risk of decompression sickness (DCS) and refer to information published by Divers Alert Network (DAN), a leading authority on dive safety.

Cannabis and THC: What Happens in the Body?

When cannabis is consumed—whether by smoking, vaping, or ingestion—THC rapidly enters the bloodstream and crosses the blood-brain barrier. Its effects on the central nervous system are mediated by the endocannabinoid system, primarily through CB1 receptors in the brain and CB2 receptors in peripheral organs and immune cells.

Key physiological and psychological effects of THC include:

• Impaired short-term memory and cognition

• Altered perception of time and space

• Reduced motor coordination and balance

• Euphoria or anxiety, depending on dosage and individual sensitivity

• Increased heart rate and altered blood pressure

• Sedation and drowsiness

  
  

These effects typically peak within 30 minutes of smoking and can last for hours, depending on the dose and method of ingestion. The impairments caused by THC present a serious concern for divers, whose safety depends heavily on mental clarity, precise motor control, and accurate judgment.

Cannabis and Scuba Diving, Dangerous for Divers

Scuba diving requires a precise synchronization of mental alertness and physical coordination. Divers must continually assess depth, time, buoyancy, gas consumption, and emergency procedures. The effects of THC—especially diminished judgment, slowed reaction time, and distorted sensory perception—are fundamentally at odds with the demands of a safe dive.

Some of the specific dangers include:

• Delayed Emergency Response In emergencies, quick thinking and action are crucial. A diver under the influence of cannabis may react too slowly to manage a malfunctioning regulator, entanglement, or signs of nitrogen narcosis.

• Poor Buoyancy Control Cannabis can impair fine motor control and balance, making it difficult to maintain neutral buoyancy. This could lead to unplanned ascents or descents, increasing the risk of barotrauma or decompression sickness.

• Distorted Perception THC affects spatial awareness and visual processing. Divers may misjudge distances or fail to notice hazards, such as currents, entanglements, or nearby marine life.

• Reduced Thermoregulation THC affects the hypothalamus, which regulates body temperature. In cold water, this could blunt the body's natural responses to hypothermia, reducing awareness of temperature extremes and increasing risk.

  
  

Decompression Sickness (DCS): Could Cannabis Make It Worse?

Decompression sickness occurs when nitrogen bubbles form in body tissues and the bloodstream during or after a dive. It is typically caused by ascending too quickly or not allowing sufficient time for nitrogen to off-gas safely.

While there is no direct study conclusively linking cannabis use to higher incidence of DCS, DAN (Divers Alert Network) warns against diving under the influence of any mind-altering substance, including cannabis. Their 2020 article, "Impairment and Diving: Understanding the Risks," outlines how impaired cognition or motor control can interfere with dive planning, adherence to decompression protocols, or recognition of early DCS symptoms—all increasing the likelihood or severity of an incident.

Moreover, some hypotheses suggest that cannabis’s cardiovascular effects—such as vasodilation and increased heart rate—could alter blood flow patterns, potentially affecting nitrogen uptake and elimination. While these mechanisms have not been studied directly in divers, similar circulatory changes are known risk factors for DCS.

A 2011 study by B. Lafaye and colleagues in the Journal of Clinical Pharmacology described THC's ability to affect vascular resistance and perfusion, particularly in the brain and skeletal muscles—two areas most commonly affected in DCS. Though not conclusive, such effects might theoretically exacerbate bubble formation or reduce the body’s ability to manage inert gas loads.

Compounded Risks: Diving, Cannabis, and Other Factors

It's critical to remember that diving rarely occurs in a vacuum. Many contributing factors can interact with cannabis use to increase danger:

• Fatigue and sleep deprivation can magnify the sedative effects of THC.

• Dehydration, often caused by cannabis use and a known contributor to DCS risk, further complicates matters.

• Altitude diving or flying after diving, especially with THC still in the system, may further impair judgment when making crucial post-dive decisions.

• Poly-drug use (e.g., alcohol and cannabis) significantly compounds impairment.

Current Recommendations from the Dive Medicine Community

While recreational cannabis is legal in many places, every major dive safety organization strongly recommends complete sobriety before diving.

• DAN explicitly advises against diving while under the influence of cannabis, citing the unpredictable effects on cognition and psychomotor control.

• The Undersea and Hyperbaric Medical Society (UHMS) also lists drug use, including marijuana, as a relative contraindication to diving.

In the absence of precise pharmacokinetic models for THC in divers (how long impairment lasts relative to depth, pressure, and gas saturation), the most conservative and safe approach is to allow at least 24 hours between cannabis use and any dive—and longer for edibles or high-dose products.

Conclusion: Majiuna and Diving Don’t Mix

Cannabis may offer recreational or therapeutic benefits topside, but its effects underwater are unpredictable and potentially deadly. Diving is inherently risky and demands full physical and mental capacity. THC’s impact on coordination, judgment, and response time is incompatible with the rigors and responsibilities of safe diving.

Whether you’re a new diver or a seasoned professional, leaving cannabis use for after the dive—not before—may save your life. Awareness, education, and responsible decision-making remain the best tools for staying safe beneath the surface.

Ocean Therapy Charters maintains a strict policy prohibiting the use of cannabis

(majiuna) and other intoxicating substances before and during diving activities—a stance rooted in safety, responsibility, liability, and adherence to established dive medicine standards.

This policy reflects a growing consensus in the diving industry, supported by organizations like Divers Alert Network (DAN) and the Undersea and Hyperbaric Medical Society (UHMS), that any substance impairing cognitive function, motor control, or physiological response significantly increases the risk of dive-related accidents and decompression sickness (DCS).

By enforcing this rule, Ocean Therapy Charters:

• Prioritizes diver safety—ensuring that everyone in the water is mentally and physically capable of handling emergencies, controlling buoyancy, and making sound decisions.

• Protects all participants—since diving is often done in pairs or groups, one diver’s impairment can endanger others.

• Maintains legal and insurance compliance, where maritime safety regulations and liability insurance policies forbid operation and participation under the influence.

Their zero-tolerance approach is not about policing lifestyle choices, but about creating a safe, professional, and responsible dive environment. Divers who have used cannabis prior to a trip will be asked not to dive, denied boarding and participation in underwater activities.

For anyone using cannabis therapeutically, Ocean Therapy Charters recommends consulting with a dive medicine professional before scheduling dives, and being fully transparent during pre-dive medical screenings.

Bottom line: Ocean Therapy Charters takes dive safety seriously—and that means no cannabis before or during any dive activity.

Resources and References

• Divers Alert Network (DAN): https://www.diversalertnetwork.org

  • Impairment and Diving: Understanding the Risks

  • Recreational Drug Use and Diving Safety

• Lafaye, G., Karila, L., Blecha, L., & Benyamina, A. (2017). Cannabis, cannabinoids, and health. Dialogues in Clinical Neuroscience, 19(3), 309–316.

• Journal of Clinical Pharmacology – Cardiovascular and neurological effects of THC

• Undersea and Hyperbaric Medical Society (UHMS): https://www.uhms.org

If you're a diver who uses cannabis and have questions or experiences to share, consult with a dive medicine specialist or contact DAN's 24-hour medical hotline.