You’re finally on that diving vacation you booked up and saved for and even though you know the rules it’s still tempting to have ‘just the one’ drink after dinner before bed time while watching the sunset or exploring the local nightlife in town. So what are the real risks with mixing alcohol and diving?
Well the obvious risk of having a drink before a dive will impair judgement leading to potentially dangerous situations: 50% of accidents happen to adults of drinking age under the influence of alcohol.
It all boils down to dehydration. Alcohol is a diuretic. The more you consume, the night before, the more dehydrated you will be in the morning. Having that greasy breakfast will compound matters as your body gets even more dehydrated dealing with digesting it.
The dehydration doesn’t stop there. It gets worse on your first and subsequent dives. The air you are breathing in the tank, has had it’s moisture content, significantly removed, during filling, further dehydrating your body. All of this adds up to having an increased susceptibility to getting a DCS, not to mention that you may experience narcosis at a shallower depth than normal.
Body temperature is another concern. Diving requires surviving in a medium where heat is pulled from our bodies 20 times faster than it is in air. So no matter what the temperature, heat loss is a concern. It’s just a matter of degree. And who hasn’t been told that a great way to fend off the cold is with a good stiff drink? After all, alcohol feels so warm going down that it certainly must rekindle the internal fire, and give us that essential extra burst of energy, right? While it may sound logical, it’s just not true. Pharmacologically, alcohol is a peripheral vasodilator, meaning that it causes blood vessels in the skin to open up more than normal. As blood flow increases to fill the expanding vessels, we experience that warm, flushed feeling. But this momentary sensation is misleading because it masks a more sinister effect.
The blood flow responsible for that “warm and fuzzy” feeling is diverted from the body core. This loss of blood saps heat from a more vital area of our body and makes us more — not less — prone to hypothermia. Moreover, alcohol depresses shivering, the major symptom warning us of the onset of significant heat loss. There’s also a possible double whammy because some recent studies out of Canada have shown that nitrogen narcosis also delays the body’s shiver response. So, a predive drink or two compounds the heat loss problem, and post-dive alcohol consumption can impede the rewarming process. How much sense does it make to spend hundreds of dollars for an exposure suit only to reduce its effect by drinking?
Bad as it is, problems don’t end with increased peripheral blood flow. Ironically, the blood vessels supplying our muscles do not dilate but constrict. This causes an increase in blood pressure, and is one reason those with hypertension are advised not to drink excessively. As muscle accounts for the greatest tissue mass in our body, this elevated blood pressure can place significant stress on the heart. Some believe this stress could be a contributing factor in the increasing number of diving accidents involving those with underlying heart disease.
Alcohol may also play a role in accidents blamed on poor physical conditioning. How so? Think back to the last time you had a few drinks. You probably didn’t feel a lot like exercising. This is partly due to mental impairment, but there’s another more direct reason for the feeling of fatigue; alcohol actually drains energy. One of the body’s primary fuels is sugar in the form of glucose, a substance produced by the liver. Alcohol consumption impedes the production of glucose, thus reducing our exercise ability far below normal. So, regardless of how you feel, an imbibing diver may be incapable of making the extra effort required to keep an unexpected situation from turning into an emergency.