Why Alcohol and Diving Don’t Mix

Even small amounts of alcohol can impair:

• Reaction time – slowing your ability to respond in emergencies.

• Judgment – leading to poor decisions underwater.

• Coordination – making buoyancy control, swimming, and task handling more difficult.

• Attention – reducing awareness of surroundings, dive limits, and buddy signals.

A study on recreational divers found significant performance impairments at a blood alcohol concentration (BAC) of just 0.04%, with divers often unaware of their reduced abilities. Even lower levels, around 0.02%, can impair concentration and decision-making. In other words, effects begin long before you “feel drunk.”

The problem doesn’t end there. Alcohol also causes dehydration, a well-known risk factor for decompression sickness (DCS). It increases heat loss, raising the chance of hypothermia, and can cause nausea and vomiting during a dive: potentially leading to dangerous, uncontrolled ascents. Worse, alcohol’s after-effects can mimic or mask DCS symptoms like fatigue, confusion, or headache, delaying treatment and increasing the risk of serious injury.

The Morning-After Myth

Many divers assume they are “fine” to dive the next morning after a night of drinking. In reality, the liver metabolises alcohol at about 0.015% BAC per hour: a slow and highly individual process. Depending on how much was consumed, you may still be legally intoxicated or at least cognitively impaired well into the following day. The bottom line: feeling okay does not mean you are fit to dive.

Beyond Alcohol: The Risk of Drugs

Alcohol isn’t the only intoxicant that endangers divers. Studies by DDRC Healthcare found that over 20% of divers admitted to using illicit drugs, with some taking them within hours of diving. Stimulants like cocaine raise heart rate and blood pressure, increasing the risk of cardiac arrest under exertion. Cannabis, the most common choice among divers, alters perception, impairs motor control, and compounds the effects of nitrogen narcosis. It also increases hypothermia risk and reduces the blood’s ability to carry oxygen.

In addition to health dangers, drug use carries legal and insurance consequences. If substances are suspected within a diving accident, insurance companies may refuse to cover medical costs such as hospitalisation or recompression therapy.

A Safer Approach

The golden rule is simple: if you’re not fit to drive, you’re not fit to dive. Most dive professionals recommend waiting at least 12 hours after drinking before entering the water—longer if you’ve had more than a casual drink.

Enjoy your dive first, then celebrate with a drink afterward. The ocean demands your full attention, and your dive buddy depends on you being alert, aware, and ready to respond.

Final Thoughts

Scuba diving opens up an extraordinary world of exploration and adventure. But it’s also a serious activity that requires sharp reflexes, situational awareness, and respect for safety protocols. Alcohol and drugs impair all of these, putting not only you but also your buddy and team at risk.

So next time you’re on a dive trip, save the drinks for after the dive. The reef will be just as beautiful, the stories just as fun, and you’ll be around to enjoy many more dives in the future.